SB 



q^5 U. S. DEPARTMENT OF AGRICULTURE, 
iO^Uc BUREAU OF ENTOMOLOGY— BULLETIN NO. 77. 



L. O. HOWARD. Entomelogist and Chief of Bureau. 



HIBERNATION OF THE MEXICAN 
COTTON BOLL WEEVIL. 



BY 



W. E. HINDS AM) W. W. YOTHERS, 

UNDER THK DIRECTION OF 

W. D. HUNTER. 



Issued October 18, 1909. 




WASHINGTON: 

GOTKRNMKNT PRINTIXTx OFFICE, 

1909. 



g[( 1S00 ig 



Class. 
Book. 



_^5 



..^<? 



N 

U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ENTOMOLOGY— BULLETIN NO. 77. 

L. O. HOWARD, Entomologist and Chief of Bureau. 



HIBERNATION OF THE MEXICAN 
COTTON BOLL AVEEVIL 



/ J 



BY 



w. E.'iriNns AM) w. w. yotiiers, 

UNDKK THE DIRECTION oF 

AV. I). Ill NTER. 



ISSUKII OCTOBKR IS, 1909. 




WASHINGTON: 

GOVERNIMENT PRINTING OFFK^E, 
1909. 






LETTER OF TRANSMITTAL 



IT. S. Department of Agricultttre, 

BiTREATT OF Entomolo(;y, 
Washmgfon, D. 0., Octoler 6, 1908. 
Sir: I liave the honor to tiansmit herewith for publication as 
Bulletin No. 77, of the Bureau of Entomology, a manuscript prepared 
by Dr. W. E. Hinds and Mr. W. W. Yothers under the direction of 
Mr. W. D. Hunter. This manuscript deals with the hibernation of 
the Mexican cotton boll weevil. The winter season is a critical period 
in the life history of this very destructive pest. An exact knowledge 
of its hibernation throws much light on practical control. For 
this reason careful experimental studies have l)een carried on for 
several years. On account of their importance tlie results are pre- 
sented somewhat in detail. The illustrations will add greatly to the 
clearness and force of the text. 
Respectfully, 

L. O. Howard, 
Entornolugist and Chief of Bureau. 
Hon. James Wilson, 

Secretary (f Agriculture. 
2 



nC\ y-' 



CONTENTS. 



Paso. 

Entrance into hibernation 11 

Supply ctf weevils to enter liibernatioii 11 

Stages entering- hibernation 13 

Time of entering hibernation 15 

Proportion of each sex among weevils in fall 16 

Numl)er of adult weevils entering hibernation 17 

Temperature conditions ])ro(lucing hilxTnation 20 

Shelter during hibernation 25 

Shelter in bolls 25 

Iliberuatiou shelter cither than Ixills within the field 30 

Hibernation shelter outside of cotton fields 31 

Hibernation experiments in small cages 33 

Cage experiments of 1 902-3 34 

Cage experiments of 1903-4 34 

Cage experiments of 1904-5 34 

Hibernation experiments in small cages, 1905-(> 35 

Large-cage experiments, Keatchie, La., 1905-6 38 

Favorable conditions for hibernation 41 

Effect of acclimatization upon survival and emergence 42 

Relation of emergence to effective temperatures 43 

Relation of time of entrance into hibernation to siu'vival and emergence. . 45 

The relationship of accumulated effective tem])eratur(> to emergence 46 

Longevity of weevils after emergence in Keatc^hie experiments 48 

Large-cage experiments Dallas, Tex., 1905-6 49 

Nature of weevil activity following emergence from hibernation 50 

Climatic conditions producing emergence from hibernation at Dallas, Tex., 

in 1906 52 

Emergence in the field at \'ictoria, Tex., in 1906 52 

Large-cage experiments, 1906-7, Dallas, ( 'alvert, and X'icloria, Tex 55 

Plan of experiments 55 

Climatic conditions producing hil^ernation and activity of w('(>\ils during 

normal hibernation period 57 

Entrance into hibernation 58 

Activity during normal period of hil)ernation (;2 

Winter activity ()4 

Activity as shown by development diu-ing normal hibernation ])eriod. ... 66 

Activity in the field during normal hil)ernation period 67 

Emergence from hibernation, 1907 67 

Relationship of emergence from hibernation to climatic conditions 68 

Effect of time of entering hibernation and nature of shelter upon tlie ])er- 

centage of survival : 74 

Survival of weevils by localities and cage sections 77 

Monthly summary of emergence records 79 

Weekly emergence records 79 

3 



4 HIBEENATION OF THE COTTON BOLL WEEVIL. 

rage. 

Longevity of weevils after emergence from hibernation 83 

Longevity of unfed weevils after emergence from hibernation 84 

Longevity of fed weevils after emergence from hibernation 86 

Bearing of ol)servations on fed and nnfed weevils on the possibility of avoid- 
ing damage to cotton by late j^lantiug 89 

Sex of weevils surviving hibernation 9i 

Secondary sexual characters 91 

Proportion of sexes sm'viving hibernation 92 

Relation of hibernated weevils to food sui)ply 93 

Summary and conclusions 95 



ILLUSTRATIONS 



PLATES. 



Page. 



Plate I. Weather-recording apparatus and fence-row slielter. Fig. 1. — 
Weather apparatus used in recording temperature and humidity 
conditions. Fig. 2. — Typical weedy fence-row, affording excel- 
lent shelter for weevils 30 

II. Favoral)le shelter conditions in and around fields. Fig. I. — Cotton 
field adjoining grove of trees laden with Spanish moss ( Tilldndsia 
usneoides). Fig. 2. — Near view of moss. Fig. 3. — Cotton stalk 
having many bolls infested by weevils at hibernation time 30 

III. Seed house and hibernation cage, Keatchie, La. Fig. 1. — Seed house 

opposite which the first sign of weevil work was found at Keatchie, 
La., in 1905. Fig. 2. — Large cage built for hibernation experi- 
ments in 1905-6 38 

IV. Hibernation experiments, Dallas, Tex., 1905-ti. Fig. 1. — Four-section 

cage used for experiments, built over cotton. Fig. 2. — Shelter con- 
ditions as occurring naturally in section 1 50 

V. Shelter conditions in Dallas, Tex., experiments, 1905-0. P^ig. 1. — 
Piled cotton stalks and piled boxes in section 2. Fig. 2. — Stand- 
ing cotton stalks versus piled leaves, section 3 50 

VI. Cages for hibernation experiments in Texas, 1906-7. Fig. 1 . — Dallas, 
Tex., cage on fiat, black-waxy land. Fig. 2. — Calvert, Tex., cage 
on slightly sloping, sandy land in post-oak region. Fig. 3. — 
Victoria, Tex., cage on sandy-loam slope between bottom and 

upland 56 

VII. Shelter conditions, Dallas, Tex., cage. Fig. 1. — Active weevils try- 
ing to escape through wire on October 20, 1906. Fig. 2. — Section 
], in which weevils were placed October 13, 1906, 2.61 per cent 
surviving. Fig. 3. — Section 4, started October 16, 1906. 4.07 per 

cent surviving 64 

VIII. Hanging moss as affecting hibernation and emergence. Fig. 1. — 
Section 7, with hanging moss in top of cage. Fig. 2. — Same sec- 
tion, ground conditions, started October 24, 1906, 6.95 per cent 
surviving; emergence ceased June 17, 1907 74 

IX. Shelter conditions producing average survival at Dallas, Tex. Fig. 
1. — Section 8, started October 30, 1906; emergence ceased June 15, 
1907; survival, 8.85 per cent. Fig. 2. — Section 5, started Novem- 
ber 5, 1906; emergence ceased May 15, 1907; survival, 12.22 per 
cent. Fig. 3. — Section 3, started November 12, 1906; emergence 

ceased May 21, 1907; survival, 14.74 per cent 74 

X. Exceptionally favorable conditions and boll experiment. Fig. 1. — 
Section 10, a, bolls exposed on surface; h, corner where bolls 
were buried 2 inches deep, started December 6, 1906; emergence 
ceased May 2, 1907; survival, 4.51 per cent. Fig. 2. — Section 9, 
stalks left, started November 13, 1906; emergence ceased June 

19, 1907; survival, 25.92 per cent 74 

5 



6 HIBEENATION OF THE COTTON BOLL WEEVIL, 

TEXT FIGURES. 

Page. 
Fig. 1. Chart showing mean average temperature, rainfall, and weevil emer- 
gence, Keatchie, La. , March to June, 1906 41 

2. Chart showing mean average temperature, rainfall, and weevil emer- 

gence, Dallas, Tex., March to May, 1906 53 

3. Chart showing mean average temperature, rainfall, and we(>vil activity, 

Dallas, Tex., October, 1906, to March, 1907 ]. 59 

4. Chart showing mean average temperature, rainfall, and weevil activity, 

Calvert, Tex., October, 1906, to March, 1907 60 

5. Chart showing mean average temperature, rainfall, and weevil activity, 

Victoria, Tex., October, 1906, to March, 1907 61 

6. Chart showing mean average temperature, rainfall, and emergence from 

hibernation, Dallas, Tex., March to June, 1907 69 

7. Chart showing mean average temperature, rainfall, and weevil emer- 

gence, Calvert, Tex., March to June, 1907 70 

8. Chart showing mean average temperature, rainfall, and wee\il emer- 

gence, Victoria, Tex., March to June, 1907 71 

9. Secondary sexual characters of Anthononins yrandis 91 



PREFACE 



Natural conditions anniiall}' reduce enormously the numbers of the 
cotton boll weevil. Although no two seasons are exactly alike, never 
more than a small percentage of the weevils in the fields in the fall is 
permitted to survive until spring. Ill fact, winter is the most critical 
season in the whole life history of the weevil. Any steps in control 
of the weevil during the winter are therefore much more important 
than those which can be taken at any other season of the year. To 
destroy ten weevils in the winter is much better thnn to destroy many 
thousands in the summer. The cotton boll weevil is now causing a 
damage in the ITnited States each year of at least $25,000,000. The 
indications are that this amount will continue to be lost for some time 
at least on account of the difficulties in control which will be encoun- 
tered in the Mississippi A^alley. For these reasons the Bureau of 
Entomology has conducted careful investigations of the hibernation 
of the weevil and presents the somewhat detailed results in this 
bulletin. 

Until this time the hibernation of the boll weevil has been less 
understood than any other phase of its life history. This was due to 
the great ditliculty in obtaining the necessary data and the fact that 
the })henomena of hibernation are not necessarily identical in different 
seasons. In fact, it will be seen from the following pages that there 
have been very important dissimilarities between the years when 
special observations have been under way. The necessary repeated 
work in large cages in different localities has now been carried on and 
extensive field observations have been made in various representative 
parts of the infested area as to the natural situations in which the 
hibernating weevils occur. As a result, the present bulletin will 
make the life history of tlu^ boll weevil during the winter season at 
least as well known as any other portion of its biology. 

In the work leading to tliis bulletin practical considerations have 
always received primary attention. However, it has repeatedly been 
shown that careful detailed investigations of injurious insects may 
residt in important suggestions for control that are not foreseen at the 
beginning of the work. Tlierefore the topic of the hibernation of the 
boll weevil has been investigated from every possible standpoint. 
Its importance, as a critical period in the life history of a most injuri- 
ous pest, has abundantly warranted this work. 

7 



8 HIBERNATION OF THE COTTON BOLL WEEVIL. 

Foremost among the points of inunediate practical application 
shown in this bulletin is the enormous importance of the fall destruc- 
tion of the plants. This has been one of the recommendations of the 
Bureau of Entomology for some years. Its importance will increase 
rather than diminish in the regions now invaded by the insect. The 
cage experiments at Dallas, Calvert, and Victoria, Tex., in the winter 
of 1906-7 have given most important anil accurate data showing 
exactly what may l)e accomplished 1)}" the fall destruction of the 
plants at various dates. This bulletin, moreover, shows the most 
favorable and least favorable conditions in the hibernation of the 
weevil. This infoi'mation can be put to practical use by every farmer 
in the infested area. It shows exactly where the most elfectivc work 
can be done. A not imimportant feature is the showing of the abso- 
lute impracticability of late planting to obviate damage by the boll 
weevil by reason of the remarkable longevity of hibernated individuals 
without any green food whatever. 

The information included in this bidletin has Ijeen accunuilated 
through the investigations and observations of the numerous agents 
connected with the work during the seasons of 19()L'-1907. Some of 
the facts have been briefly stated in previous publications, particularly 
Bulletins 45 and 51. The manuscript for the present publication was 
prepared during the summer and fall of 1907, and since that time 
some of the conclusions drawn from this study have been published in 
connection with other bulletins and circulars relating to the weevil 
and its control. But in no other instance have all of the facts been 
considered or their complex, intimate, and important co-relationships 
studied as in this work. 

On account of the large amount of work that has been done and the 
practical importance of many of the conclusions drawn it has been 
considered that full indication should be made in the bulletin of the 
methods by which the conclusions and recommendations are reached. 
Therefore special pains have been taken to give all essential data and 
to represent by charts matter that can thus be graphically expressed. 

It will be noted that the various experiments dealt with in this 
bulletin are taken up according to the years in which the work was 
carried on. The result is that some special topics, such as time of 
entrance into hibernation, will be found discussed in several places. 
It has been found entirely impracticable to follow a strictly topical 
system and discuss each point connected with hibernation with refer- 
ence to the work of the various years. This impracticability is due 
principally to the great natural variations in the seasons. Never- 
theless the first part of the bulletin discusses the general feature of 
hibernation and the summary at the end has been written in such a 
way as to bring the prmcipal conclusions on the various topics into 
condensed form. 



PREFACE. 9 

The question of credit to the various investigators who have con- 
tributed to tliis bulletin is rather complicated. Air. E. A. Schwarz 
studied carefully the hibernation of the weevil at A'ictoria, Tex., in 
the winter of 1901-2 and his observations have been utilized. Later 
Mr. Wihnon Xewell, secretary of the State Crop Pest Connnission of 
Louisiana, assisted by Air. J. B. Garrett, planned and executed a 
series of experiments in the hibernation of the weevil which was much 
more extensive than any similar work that had l)een done up to that 
time in this country. This work was done in coojxM'ation with the 
Bureau of Entomology, and the results, througii the liberality of 
Mr. Newell, have been largely incorporated into this bulletin. Air. 
J. D. Alitchell contributed important facts from observations during 
severaj seasons, especiall}" with reference to actual winter Held con- 
ditions. Many of the details in the plans for the extensive work of 
190G-7 were worked out l)y Dr. W. E. Hinds, wlio also superintended 
the extensive tedious work necessary during the follovving spring. Li 
all this work Doctor Hinds was assisted by Air. AV. AV. A'others, by 
Air. A. C Alorgan, who h;id charge of the work with the large cage 
near Alctoria, and by Air. C. K. Jones, who was located at Calvert. 
Air. A'others collaborated with Doctor llintls in the arrangement and 
correlation of the data obtained at the places mentioned and in placing 
in manuscript form the records of many of the experiments of previous 
years. For two winters Air. Yothers carried on sp(>cial observations, 
largely of his own planning, as to actual iiehl conditions. In this 
work he collected large quantities of bolls and various forms of trash 
in and about cotton fields, and from careful examinations of this 
material in the lal>oratory he was al)le to determint^ many vcn-y impor- 
tant facts in regard to the several classes of rubbish, or winter shelter, 
which are most likeh' to protect weevils and to insure their successful 
siu'vival through the winter season. 

^Y. D. Hunter, 
1)1 Cluirge of SoutJicrn Fuld Crop 

Insect IiiVi siUjatlovs. 



HIBERNATION OF THE MEXICAN COTTON BOLL 

WEEVIL. 



ENTRANCE INTO HIBERNATION. 

In the study of hibernation of the ]\Iexican cotton boll weevil 
(AntJionomus grandis Boh.) we shall first consider the factors affect- 
ing the abundance of weevils which may enter hibernation, the 
dependence of the number of weevils present upon precediiig con- 
ditions of food supply, the climatic conditions accom])anying or 
producing the beginning of hibernation, and other biological facts 
which may be of interest or value in connection w^ith this division 
of the subject. 

SUPPLY OF WEEVILS TO ENTER HIBERNATION. 

The common name ''cotton boll weevil," which is uniformly 
applied to this insect, may be in part at least responsible for a mis- 
leading impression in regard to the most common i)oint of attack 
and place of development of tins weevil. The common name was 
first a})plied because of the fact that in the first recorded case of this 
insect attacking cotton the specimens were found in bolls. It is a 
fact, however, that by far the greater number of weevils to be found 
in any field at any season of the year have really developed witliin 
the buds or squares rather than within the bolls. In the first place, 
it is perfectly evident that during the entire growing season of the 
plant, in the infested area, pi'obably not much more than 10 })er cent 
of the squares which form idtimately produce bolls. For this reason 
the weevils find opportunities for reproduction many times greater 
in squares than in bolls. In the second place, a careful study of the 
habits of the weevils shows that they prefer squares both for feeding 
and for reproduction. In the third place, the average ])erio(l required 
for development in squares is oidy one-half to one-third as great as 
it is ill bolls which become more than one-half grown. These three 
considerations insure a far more rapid and abundant nudtiplication 
of individuals through the medium of squares than through bolls. 
Wherever weevils have been present in average abundance at the 
beginning of the season, unless tliey have been unusually checked 
by climatic conditions unfavorable to their develoj)ment, a condition 
of total infestation of squares is usually reached between August 1 

11 



12 HIBERNATION OP THE COTTON BOLL WEEVIL. 

and 20. By this time practically all of the crop which can be expected 
will have been set and man}^ of the oldest bolls will be found maturing. 
If a moderate crop of bolls is being matured the formation of squares 
usually ceases, almost if not entirely, for a period of several weeks. 
Whereas in the early })art of the season female weevils could find 
abundant opj^ortunities for depositing their eggs in previously unin- 
fested squares, after the time of total infestation is reached such 
opportunities practically cease to exist. The available supply of 
squares and bolls becomes too small to support the large muiiber of 
weevils which may be present, and conditions become decidedly 
unfavorable for their further multiplication. It is at this season of 
the year, nsually from August 15 to September 20, that the largest 
general dis]:)ersion movements of the weevils take place. It is at this 
season also, during recent years, that the cotton leaf-worm has 
become sufhciently al)undant to secure a partial or complete defolia- 
tion of the ])lants. While the occurrence of the leaf-worms is by no 
means regular, the effect of their work is to still further limit the 
availal)le food supply of the boll weevil and to force them into a more 
general dispersion from the defoliated plants. On account of the 
reduced su{)ply of squares, the increased period of development in 
bolls, and the extensive dispersion movements of the weevil at this 
season of the year, it usually happens that the actual nuniber of 
individuals in a field becomes greatly reduced. 

Following the maturity of a considerable portion of the crop of 
bolls, and usually in connection with the occurrence of a heavy rain- 
fall, a renewed growth of the plant commonly produces an abundance 
of squares. It is this late top growth of the j)lant, which serves no 
good purjiose so far as further production of cotton is concerned, 
that is primarily responsible in most fiekls for the needlessly large 
number of weevils produced between the time of maturity of the 
crop and the usual time of destruction of the plants by frost. A 
large proportion of the weevils which become adults before Septem- 
ber 1 may be expected to die, either as cold weather comes on or 
during the early part of the winter season. The later-developed 
weevils, however, have not exhausted their vitality and are much 
more likely to survive the full hibernation period. The importance, 
therefore, of preventing or of reducing the formation of squares 
following the period of maturity of the bolls can be easily appreciated. 

To sum up briefly the principal points in the development of 
weevils which may enter hibernation, we may say that from the 
beginning of the formation of squares until the plants are destroyed 
by frost the development of the boll weevil is a continuous 
process. During the usual fruiting period of the plant it is possible 
that as many as eight generations of the weevil may be produced, 
especially in southein Texas. It is also possible that during this 



ENTRANCE INTO HIBERNATION. 13 

period individuals in:w exist which represent an advance of only 
one generation. During the entire season the average period required 
for development, in squares, from the deposition of the egg to the 
emergence of the adult weevil is from 18 to 20 days. In l)olls the 
developmental period may exceed 60 days. The average period 
during which each female may deposit eggs is hetween 50 and 60 
days. The average number of eggs which each female may be 
expected to deposit is not far from 100. The average ])erio(l required 
for each generation is between 40 and 45 days. In southern Texas, 
therefore, five full generations of the weevil may usually be expected, 
and owing to the somewhat shorter season and lower t(un])eratures 
occurring in northern Texas four generations is |)r()l)ably (he true 
average in that section of the State. There is no jiarticular hiber- 
nation brood, but representatives of all generations may survive 
and enter hil)ernation. Froui these considerations it will be readily 
understood that during the latter part of the season the multiplica- 
tion is primarily dependent upon tlie food supply, and that the com- 
mon practice of allowing stalks to stand after the crop becomes 
matured is primarily responsible for a large proportion of the weevils 
which may enter hil^ernation. 

It is but repeating statements which have been frequently made 
in former publications of this investigation to say tliat the vain 
hope of securing some top croj) of cotton, in case there should be a 
late fall, is probably the prini-i})al reason which has been urged for 
allowing this growth of the plant. So far as we know there is no 
record of a top crop ever having been secured in a field which had 
become tlioroughh^ infested with boll weevils earlier in the season. 
"V\niile it is true that in uninfested regions some top crop has occa- 
sionally been formed and may occasionally be secured in the future, 
i( is not putting the facts too strongly to say that within the weevil- 
infested area this has never occurred and shoidd ncA^'r be expected. 

STAGES ENTERING HIBERNATION. 

The reproductive activity of the weevil continues steadily until 
the plants are destroyed by frost. It gradually decreases coinci- 
dently with the gradual decrease in heat. All stages from the egg 
to the adult maybe found in both squares and bolls, even after frosts 
have occurred. The immature stages in squares are not immediately 
killed unless the fi-eeze is exceptionally severe, but probably very 
few of these survive to reach maturity and to emerge during the 
following spring. Only those which are nearly adult at the time 
frost occurs may be expected to emerge. These might emerge upon 
warm days following the colder weather, but in the absence of a 
fresh food supply would soon die. In the fall of 1903 Prof. E. D. 
Sanderson records, from an examination of 700 squares at the middle 



14 IMI'.IMtNATTON OF THE COTTOiS: BOLT. WEEVIL. 

of November, iintliiii^ 79 eggs, or tliat 11 per cent of the squares 
contained eggs. From an examination of 1,600 scjuares he states 
that 366 hirva^ were found, showing tliat about 2o per cent of the 
squares contained hirv« at the time of entrance into hibernation. 
Some stages may survive in squares for a short time after the freeze, 
but there are few records of weevils entering hibernation at immature 
stages in squares and surviving to emerge therefrom in the spring. 
These stages are therefore unimportant from an economic point of 
view. 

Witli immature stages entering ]iil)ernation in bolls (PI. II, fig. 3) the 
case is (piite (hlFcnvut from that in squares. Extensive examinations 
have ])een made at various times in wi(U>ly separated localities to deter- 
mine the ])ossil>ility of these stages maturing in the bolls (huing the 
winter and emerging in the spring. About the middle of Novend)er, 
in the winter of 190;5-4,it was sufficiently cold at ^'ictol•ia to destroy 
cotton plaids. By the last week in December two hard frosts and 
one freeze had occurred, but at that time living larva>, })upa% and 
adults could ])e very commoidy foinid in imopened bolls. Two 
weeks later, upon making another examination, IMr. J. D. Alitchell 
found a smaller proportion of larvae with more pupse and adults. 
Examinations were also made on January 17 and 31 and February 
4 and 17, 1904. In the course of these examinations 23 larva?, 30 
pupse, and 144 adults were found, and most of them were living. At 
Terrell, Tex., on December 15, 1904, in examinations of 200 bolls 
Mr. C. li. Jones found 101 larviP, 16 jiupcTp, and 4 a<hdts, all of which 
were alive. Fifteen days later, in examining 100 dry bolls, he found 
20 larva?, 16 pupa^, and S adults. Sixty per cent of the larva% S7.5 
per cent of tlie i)U])a^, and 62.5 })er cent of the adults were alive on 
Deceml)er 30. On ffanuary 7, 1905, in an examination of '300 dried 
bolls 29 larva', 19 pupa^, and 1.") achdts were found, while the per- 
centage of living, in each stage, had fallen to 17.2 for larva?, 15.8 for 
pupa-, and 7.7 for adults. At Wharton, Tex., after the middle of 
November, 1905, an examination of 52 bolls disclosed 30 larvae and 
2 pup«, all of which were alive. 

These records might easily be multiplied, but it is unnecessary 
to do so to ])r()ve that very large numbers of weevils enter upon the 
l)eriod of hibernation as immature stages and that during many 
seasons, especially in the southern part of the State, a large per- 
centage of these complete their development, and that many weevils 
may survive until time for their emergence in the spring. This 
point is emphasized especially because of its significance in regard 
to the most advisable method for destroying the stalks together 
with the infested unopened bolls which may remain upon them 
late in the season. Upon page 26 will be found records showing the 
results of extensive exannnations of bolls duiing the winter and 
early spring, whicli add much emphasis to this point. 



ENTRANCE INTO HIBERNATION. 15 

TIME OF ENTERING HIBERNATION. 

Before (lisonssing- the question of the time at which weevils usually 
"enter hibernation" it seems desirable to explain the sense in which 
that term is used. The action of the weevils in securing slielter from 
approaching cold is not intelligent. It is probably true that they 
have no such sense of sight as wc commonh^ understand from the 
use of that word and that their selection of shelter is not at all 
guided by that sense. We mean by this that a weevil on a cotton 
plant can not see at an}' distance shelter which might be attractive 
to it and thereupon fly fi'oin the plant to the slielter. It is true that 
cold nights with a temperature between 40° and 50° F. succeeded 
by warm still days, such as occiu' conuiK)nly in the fall, do seem to 
stimulate the weevils to an unusual activity both in flight and in 
crawling. It may be true that they have an instinctive knowledge 
of the approach of tempei'ature conditions from which the}' must 
secure shelter, but it is also true that many weevils remain active 
upon plants for some time jifter the plants have been tlestroyed by 
frost and frequently until several weeks after other individuals 
have entered hibernation. In speaking of entering hil)ernation, 
therefore, we mean the entrance of the weevils upon a period of 
comparative if not complete inactivity. Their action in seeming 
shelter is gradual and governed primarily by the degree of protec- 
tion from the cold which they may receive. If early in the season 
a weevil accidentally finds shelter which gives it exceptional pro- 
tection from the cold it will likewise be exceptionally protected from 
heat, and therefore less likely than are other less fortunate indi- 
viduals to resume its activity upon warm days. If at first the 
shelter which weevils find is but slight, they will be easily influenced 
by succeeding warmth, and in another period of activity will be 
likely to find better protection. Their flight upon warm days un- 
doubtedly leaves large numbers of them outside of the cotton fields, 
where they are as likely to find favorable shelter as within the fields 
themselves. 

From this explanation it will be understood that it is rarely pos- 
sible to indicate by a single date the time when weevils enter hiber- 
nation. It may be better expressed as a period within the limits 
of which a large majority, though possibly not all, weevils may seek 
shelter. Naturally this time varies according to the seasonal tem- 
perature conditions, so that in one locality it may occur several 
weeks earlier in one season than in another. It is also evident that 
differences in temperature conditions due to latitutle or altitude will 
cause a similar variation in the time when weevils enter hibernation. 
In the following paragraph are given the approximate dates which 
have been determined for this event at various localities since 1902. 



16 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



At A'ictoi'ia, Tex., largo numbers of weevils were still active in 
the fields about the midtlle of December, 1902, at which time direct 
obsei-vations were discontinued. It is probable, however, that 
weevils were gradually seeking winter quarters at any time after 
tlu^ first of that month. Prof. E. D. Sanderson states that at College 
Station, Tex., in 1903 weevils did not enter hibernation until after a 
freeze which occurred on November 18. After this date they soon dis- 
appeared. Tn 1903, at Victoria, hibernation began between Novem- 
l)er 15 and 30. At several points between College Station and Terrell, 
Tex., in 1904, hibernation began about November 10 and was not 
complete until (>arly in December. During this same year at Victoria 
it occurred (hiring the ])erio(I from November 11 to about December 
S. The following y(nir at Victoria it did not occur until after Decem- 
ber 15, while in 1906 at the same place weevils entered hibernation 
between November 9 and 20. At Dallas, Tex., in 1905, few weevils 
entered hil)ernation l)efore the end of November, when heavy frosts 
occurred, but they disap]ieared in the fields during the first few days 
of December. At Dallas in 1906 weevils entered hibernation between 
November 15 and December 1. 

These conclusions as to the approximate periods when weevils 
entered hil)ernation are based u])on field ol)servations which showed 
the gradual disappearance of the weevils from the plants. The con- 
clusions from field observations are supported, also, by those from 
cage experiments. 

PROPORTION OF EACH SP:X AMONG WEEVILS IN FALL. 

Determinations of sex proportion among weevils in midsummer 
have shown that during that period the sexes exist in approximately 
e([ual numbers. As the development becomes retarded l)y a]iproach- 
ing cold weather there seems to be a tendency toward the production 
of moi'e males than females. The generally longer life of males may 
also account in part for the increased proportion of that sex, which 
is shown in the following table: 



Tahle I. — Proportion of in ale uiuljt'inale weevils at time of enter iiuj hibernation. 



Year. 


Male. 


Female. 


Number. 


Per cent. 


Numlier. 


Per cent. 


1004 


557 
63 
173 
173 
19 
31 
29 


63. 7 
57. 7 


317 
127 
78 
127 
14 
19 
26 


36.3 
42.3 


1905 


1906 


1906 ... . 


57. 6 
62.0 
52. 7 




1906 


42.4 
38.0 
47.3 


1901 


1906 




1,045 


60. 


70S 


40.0 



ENTRANCE INTO HIBEENATION. 17 

From this record it appears that at the time of enterino; hiberna- 
tion male weevils largely predominate, being in the proportion 
approximately of 3 males to 2 females. 

NUMBER OF ADULT WEEVILS ENTERING HIBERNATION. 

It is evident that determinations bearing upon the number of 
adult weevils entering hibernation must in all cases be largely in 
the form of estimates because of the physical impossibihty of making 
a thorough examination of more than a comparatively small fraction 
of an acre. In our own determinations upon this point we have fol- 
lowed the general plan of selecting average crops of plants in four 
or five difl'erent portions of the field, representing, so far as may be 
possible, different conditions in the growth of the plants which may 
influence the number of weevils to be found. The number of plants 
per acre is ultimately the basis upon which the estimate as to the 
number of weevils per acre is based. It is evident that the number 
of plants will vary widely in different localities. For example, in 
the river valleys, where the growth of the plants is rank, the average 
number may be about 5,000; whereas upon poorer land, where plants 
never become large, the number per acre may be as great as 10,000. 
From estimates made upon several hundred fields during the past 
two years it appears that the aveTage number of ])lants per acre is 
not far from 7,000. We beheve that this method of estimating 
the number of weevils per acre is more desirable and reliable than an 
estimation of the number of weevils per plant in which the fractions 
found in an average must be disregarded. 

In the fall of 1903 Prof. E. D. Sanderson found from his own obser- 
vations and from reports of correspondents an average of from one 
to two weevils per plant. In the fall of 1904 an examination of 
four fields at Terrell, Tex., showed a variation of between 762 and 
over 29,000 weevils per acre. This wide variation was due primarily 
to the effect of defoliation by the cotton leaf-caterpillar in one field, 
that having the exceptionally large number of weevils not having been 
defoliated. These points are mentioned particularly to show the 
wide variation which may occur within very short distances and also 
to emphasize the effect of the work of the leaf-worm in accompHsh- 
ing what is practically a more or less complete destruction of the 
stalks. 

90317- Bull. 77—09 2 



18 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



Table II. 



-(hunts to determine number of weevils per acre ul time e>f entrance into 
hibernation, in three localities in Texas. 



Date. 



Locality. 



Plants 
per acre. 



Plants 
exam- 
ined. 



Weevils 
found. 



^^'eeviIs 
per acre. 



Remarks. 



1904. 

Nov. 8 
Nov. 9 
Nov. 10 
Nov. 14 



Nov. 16 

Do.... 

Do.... 
Nov. 17 

Do... 

Do.... 
Nov. 18 



1905. 
Nov. 14 

Do.... 

Do.... 

Do.... 

Do.... 
Nov. 27 



Terrell . 



.do. 



Averages and totals. 



Calvert . 

do.. 

....do.. 
....do.. 

do.. 

do.. 

....do.. 



Averages and totals. 



AVharton. 
....do... 
....do... 
....do... 
....do... 
....do... 



Averages and totals. 



10,890 
10,890 
10,890 
10,890 

10,890 



7,200 
7,2ti0 
7,200 
7,260 
7,260 
7,260 
7,260 



7,260 



100 
100 
70 
50 



240 



267 
61 
5 



29,076 

6,643 

762 

1,742 



11,570 



4,840 



6,200 


46 


47 


6,. 355 


6,200 


66 


22 


2,073 


6,0S0 


5 


48 


58,368 


6,200 


10 


46 


28,520 


6,200 


10 


16 


1,000 


7,000 


2 


25 


50,000 


6, .313 


139 


204 


9,266 



Not defoliated liy leaf-worm. 
Defoliated. 

Do. 

Do. 

Average four fields examined 
at Terrell. 

Defoliated. 

Do. 
Not defoliated. 
Defoliated. 
Defoliated once. 

Do. 
Defoliated. 

Average seven fields exam- 
ined at Calvert. 



Not defoliated. 

Do. 
JIanv squares. 

Do. 
Grazed by cattle. 
Estimate reduced . 

Average six fields examined 
at Wharton. 



In connection with the work done at Dallas diirinoj the fall of 1906 
repeated estimates of the number of weevils per acre to be found 
upon the stalks were made in the same field beoinning October 12, 
1906, and ending January 21, 1907. These figures are presented in 
Table III. The number of plants per acre in this field was 8,300. 

Table III. — Number of weevils per acre upon stalks at different dates at Dallas, Tex. 



Date. 


Plants 
exam- 
ined. 


Living 
weevils 
found. 


Living 
weevils 
per acre. 


1906. 
Oct. 12 


110 
84 
60 
35 
35 
36 
35 

35 


122 
190 
106 
29 
27 
10 
5 

3 


9,205 
18,774 
14,663 
6,877 
6,403 
2,. 306 
1,186 

711 


Oct. 31 to Nov. 3 

Nov. 10 


Nov. 20 


Nov. 22... 


Dec. 1 

Dec. 18 

1907. 
Jan. 21 



The table given above shows a number of points which are of 
exceptional interest. About November 1 it may be seen that the 
number of weevils present was mcn-e than double the number of plants. 
After that time there was found to be a steady decrease in the number 
of weevils present upon the stalks. The most abrupt change was 
to be found between November 10 and 20, when more than one-half 



ENTRANCE INTO HIBEENATION. 19 

of the weevils seem to have left the plants. This decrease may be 
attributed to several factors. First, the weevils were (gradually 
leavinw the plants throuoh flight, which may have carried them out- 
side the fields, and, second, many were seekino^ and remainino; in 
shelter which was to be found upon the ground within the field. A 
hard freeze preceded by low temperatures during several days occurred 
on November 19. However, the examinations made on November 
20 and 22 showed many weevils present in the frozen squares and 
especially upon the bolls. It is apparent that these weevils <lid not 
immediately leave the plants, but remained upon the bolls and 
squares as long as the latter might serve as a food supph^ But 
within a few days all scjuares and foliage became perfectly dry, and 
after this especially weevils became less active. The numbers which 
were found upon the plants after December 1 may be considered in 
a rather strict sense as in hibernation. The shelter which they could 
obtain was comparatively slight, and in the last examination, made 
on January 21, about 25 per cent of the weevils found upon the bolls 
still hanging to the stalks were dead. 

In reference to Table II attention may be called to the exceptionally 
large number of weevils found at Wharton in one field on November 
14. This was a field of about 5 acres in extent, antl at the time it 
was exannned the plants were exceptionally large and very luxuriant 
in growth, showing an abundance of squares. Very few bolls had 
been set, so that the entire growth of the plants seems to have been 
turned to the production of s([uares. As has been shown in pre- 
ceding paragraphs, such conditions would favor (Hrectly the produc- 
tion of an abnormally large number of weevils per acre. The fact 
that more than 6,000 weevils were actually collected in this field 
makes it even more certain that the estimate given, while possibly 
high, is not impossible. It may be considered as representing fully 
the maximum number of weevils which it is possible for an acre of 
cotton to support even under coniHtions which are most favorable 
to their development. Another series of examinations made before 
and after the freeze referred to at Dallas in a preceding paragraph 
should be considered in connection with Table III as serving to show 
the correlation between the disappearance of the w^eevils from 
the plants and their occurrence under shelter on the ground during the 
period when they are entering hibernation. 



20 HIBERNATION OF THE COTTON BOLL WEEVIL. 

Table IV. — Number of weevils under rubbish on ground at Dallas, Tex. 



Fioia. 


Dale e.\- 
ainined. 


Portion 

of aere 

e.xamined. 


Weevils 
found — 


Total 
per acre. 


Percent- 
age 
alive. 


Remarks. 




Alive. 


Dead. 




A 

A.. 


1900. 
Nov. 1.^) 

.do 


22 plants. 

1/204 
1/347 
1/204 

10/8384 
10/0230 
10/8384 


4 

4 
8 
5 

5 
1 
2 







14 

2 
1 
2 


1,450 

1,050 
2, 770 
5,010 

5,870 
1,247 
3,364 


100.0 

100.0 
100.0 
26.3 

71.4 
50.0 
50.0 


In Cracks of ground around bases 

of plants. 
Under rubbish on ground 


A 

A 

B 

C 

C 


Nov. 22 
Dec. l.s 

1907. 
Jan. 11 
Jan. 29 

.do 


Do. 
Do. 

Northeast corner of field. 

Middle of field. 

Near southwestern edge. 







The sum total of weevils found both oh plants and on the ground 
on November 22 shows an average of slightly more than 9,000 weevils 
per acre, all of which were alive. On December 18 the number that 
could be accounted for was between 6,000 and 7,000 per acre on the 
same, ground which had been previously examined. On the former 
date more than two-thirds of the weevils were still upon the plants. 
On the latter date nearly five-sixths of them were on the ground and 
among those on the ground but 26 per cent were living. These fig- 
ures show that between November 22 and December 18 a very large 
mortality had occurred among weevils which had entered hiberna- 
tion and esjiecially among those which had sought shelter under rub- 
bish upon the surface of the black-waxy soil of field A. 

There is some evidence indicating that there is normally a greater 
mortality among the weevils hibernating at the surface of heavy 
black soil than that occurring among weevils which hibernate on the 
surface of sandy soil. The reason for whatever difference there may 
really be in this mortality would seem to be quite directly attributa- 
ble to the difference in drainage conditions in the two types of soil, 
and to the characteristic adhesiveness of the black type. It is quite 
likely that the difference is sufficient to justify different methods of 
treatment for the two classes, but our knowledge of the constant 
variations and the effective factors is not yet sufficiently complete to 
justify us in making specific recommendations. 

TEMPERATLTRE CONDITIONS PRODUCING HIBERNATION. 

It is evident that the exact time at which weevils begin to enter 
hibernation, and that at which the entrance into hibernation be- 
comes complete, can be determined only approximately. The evi- 
dence consists largely of observations showing the decrease in the 
number of weevils which are active, the finding of weevils in a quiet 
condition within various classes of shelter, the changes in activity of 
weevils confined in cages, the cessation of feeding and of reproductive 



ENTEANCE INTO HIBERNATION. 21 

.activity, and the general relationship of temperature to conditions of 
food supply and weevil activity. In the following tables are shown 
the maximum and minimum temperature occurring throughout the 
period, which has been approximately determined for each of the 
localities indicated in the respective seasons. The maximum tem- 
perature is given above and the minimum temperature below the line 
for each day. Wlierever the climatic records for a particular locality 
are incomplete it has been necessary to use those for some other near-by 
locality. The table shows at a glance the daily range of temperature 
in each case, which undoubtedly has considerably more significance 
in regard to the entrance of weevils into hibernation than would the 
figures showing simply the mean daily temperature. The table as 
arranged shows a comparison of the records of all localities during 
each season successively. 



22 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



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ENTRANCE INTO HIBERNATION. 



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2; 




















































































































^ 




























b 




























o 






t. 






















•"" 






f 








y 








>- 










L) 


H 




D 




a 




0) 






t^ 


•£ 


H 


ci 


fH 


ca" 
























'^ 


tfi 


Lri 


Cfi 


(-. 








o 


i2 


o 


_g 


o 






t-H 






+^ 












.g 


■cs 


o 


"3 


o 






H 


> 


Q 


I-* 


G 


> 






'I* 


-^ 


lO 


i.O 


CO 


•CO 




QJ 


O 


o 


o 


o 


o 


o 




>H 


c 


H 


c 


H 


c 


2 


cr 




o 




a 


1 



24 



HIBERNATION OP THE COTTON BOLL WEEVIL. 



This table serves (o show in a graphic way the extent of the period 
of entrance into hibernation, the varying dnration of the period 
for the same k)caHty in (UlTerent seasons, and the generally later 
date of entrance in southern localities as compared with more northern 
localities in the same season. It also shows the duration of the 
period as compared with the mean average temperature prevailing. 
In general it appears that the greater the drop in temperature the 
shorter will be the period of entrance into hibernation. 

Table VI. — Periods of entrance into hibernation, and temperatures. 



Year. 



Period. 



Limits. 



Days. 



Temperature. 



Mean 
average. 



EfEective.a 



1903.. 
1903.. 
1904.. 
1904.. 
1905.. 
1905.. 
1906.. 
1906.. 



College Station, Te.x 

Victoria, Tex 

Corsicana, Tex 

Victoria, Tex 

Dallas, Tex 

Victoria, Tex 

Dallas, Tex 

Victoria, Tex 



Nov. 15-27 

Nov. 15-30 

Nov. lO-Dec.5. . 
Nov. 11-Dec. 8.. 
Nov. 29-Dec. 8.. 
Nov. 30-Dec. 18. 
Nov. 12-Dec. 8. . 
Nov. 9- Dec. 21.. 



49.5 
53.0 
55.0 
57. ^5 
40.5 
50.0 
53.0 
60.4 



6.5 
10.0 
12.0 
14.5 
None. 

7.0 
10.0 
17.4 



a In studjMng the relationship of temperature conditions to weevil activity the tenn "effective tem- 
perature " is used to designate the excess of temperature above 43 degrees F. It has been estimated that 
43 degrees marks approximately the beginning of activity with most animals, and experiments have shown 
that this is equally true of the boll weevil. Below this temiioruture the weevils are usually inactive. 
Above it they may move, feed, and reproduce with increasing rapidity as the tem])('rature increases. From 
this explanation it may be readily undeistood that the coluuui showing the decrca.se of elfective tem- 
perature is really the niost significant in connection with the inactivity or hiljernation of the weevil. 

It is undoubtedly true that minimum temperatures have a special 
influence in checking the activity of the weevil in spite of the fact 
that they may be below^ 43 degrees F. When the temperature falls 
to 32 degrees or lower the food supply of the weevils is usually rather 
completely destroyed, and this fact may serve to discom-age subsequent 
activity on the part of the weevils, even though the temperature 
conditions might otherwise favor it. 

From this table it may be seen that the shortest period of entrance 
into hibernation of which we have record is ten days. This occurred 
at Dallas, when the mean average temperature was 9 degrees lower 
than that for any other period which has been studied. 

In regard to the limits assigned to the period for Victoria in 1906 
it may be stated that hibernation was probably only partial at that 
place at any time during the winter of 1906-7. The limits of the 
period that have been given are based on field notes made about the 
middle of November indicating the beginning of the period, and 
temperature records covering the coldest period that occurred during 
December. The mean average temperature during November for Vic- 
toria was 60.4 degrees, the range being from an absolute minimum of 
27 degrees to an absolute maximum of 84 degrees. The temperature 



SHELTER DURING HIBERNATION. 25 

fell below 32 degrees only once during this month. From December 
1 to 21 the mean average temperatm-e was also 60.4 degrees. In 
this case the range of temperature varies from an absolute maximum 
of S3 degrees to an absolute minimum of 32 degrees, the latter occm-- 
ring only once. From these records it is apparent that the climatic 
conditions were not sufficiently severe either to destroy absolutely 
the food supply of the weevils. or to insiu-e the continued inactivity 
of those which may have sought shelter during the sliort periods of 
cool weather. Sprout cotton was exceptionally abundant tliroughout 
the winter and weevils were found feeding upon it almost continuously. 
From these facts we may be justified in concluding that a mean 
average temperatm-e of 60 degrees is too high for the complete hiberna- 
tion of the weevil; that hibernation usually takes place coincidently 
with the decrease in mean average temperature to about 55 degrees; 
and that it remains complete until the mean average temperature 
subsequently rises to above 60 degrees. 

SHELTER DURING HIBERNATION. 

Wliile many weevils seek hibernation shelter outside the field it 
is certain that a considerable number of them remain very near theh 
food supply — that is, in the cotton fields and in the immediate 
vicinity. Because of the difl'erences in the nature of the weevil shelter 
and in the possibility of destroying or remo^^ing such favorable 
shelter, within and without the cotton fields, these two conditions 
will be considered separately. 

SHELTER IN BOLLS. 

Within the cotton fields weevils are sheltered primarily in the 
hanging cotton bolls, the fallen foliage, and grass or other rubbish 
which may have accumulated upon the surface of the ground. 
Attention has alreatly been called to the fact that many stages enter 
the period of hibernation in an immature condition in unopened 
bolls. (See p. 14.) That many adult weevils hibernate entirely 
within the protection afforded by the bracts and hulls of bolls has 
been abundantly demonstrated (PI. II, fig. 3). Rather extensive 
experiments have been made upon this point in a number of localities 
during several seasons. The principal data resulting from these 
investigations are presented in the following two tables. Table VII 
shows a comparison of the records for several localities during four 
months of the winter of 1904-5. Dm-ing this period the prevailing 
climatic conditions were the most severe that the weevil has en- 
countered since invading Texas. The table shows therefore a 
gradual decrease in the number of living stages present as the season 
advanced. 



26 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



Tablk VII. — Dcrnasc in, pcrcctiUiyc dJ stages siirvivi.ny in bolls from December, VJO4, 

to March, litof). 





December. 


January. 






Stages alive. 










Stages alive. 














s 












a 












Adults. 




W) 








Adults. 


•3 
be 


ti 


Locality. 










c 












C 


.g 




Id 











> 


;::; 


V. 






e 




> 


> 










^ 

M 


e 


■a 


1 


3 








e 


y 


■^ 














s 




















0) 


si 


iB 


s 


i-t 


rill 


m 


03 


a 


ffi 


a 

0) 


» 
M 


.G 










ft 
































a 














a 











c3 


S 














tS 


^ 













« 


hJ 


Ph 


1^ 


w 


w 


Ph 


« 


h-1 


flH 


'^ 


w 


m 


(^ 














P.ct. 


P.d. 












Per ct. 


Per ct. 


Terrell, Tex 


300 


113 


30 


9 





48 


92 


3, 678 


38 


16 


3 


6 


1.98 


7.3 


















1,120 


3 





2 


3 


.70 


26. 


Dallas, Tex 



















Calvert, Tex 


150 


10 


1 








7 


91 


2,100 





1 


1 


10 


.50 


10. 
















































3,257 


11 


7 


9 


18 


1.37 


61.0 




















Totals and 


























averages.. 


4.50 


123 


31 


9 





36 


91 


10, 155 


52 


24 


15 


37 


1.15 


11.8 









February. 












March. 










Stages alive. 








Stages alive. 


























s 




























Adults. 


th 








Adults. 


tb 


Locality. 


■d 








.3 
> 


.g 


-d 






















.> 


































PI 






'2 




to 


tS 


.g 










bJ3 


T3 




a 






b/l 


e 


_c 


§ 


a 








e 


.a 


fl 
3 


































y, 


ai 


ft 


y 


3 


,i5 


a 


y, 


si 


si 


a 


0) 




a 










a 














a 











(S 


3 













(3 


;3 













fq 


1-1 


Ph 


'4i 


w 


m 


fi. 


n 


1-1 


Ph 


'A 


w 


pq 


F^ 














Per ct. 


Pfr c/. 












Per ct. 


Per ct. 


Terrell Tex 


1,500 
1,4.'')() 


9 


2 




1 






0.26 
.34 


1 5 
















Keatchie, La 


15 


208 

















6 


















100 
2, 176 

























Calvert, Tex 


800 























Palestine, Tex. . 
















1,599 
1,438 








(1) 

















Victoria, Tex.... 


2, 746 


4 





3 


3 


.36 


8.6 





Totals and 






























averages. . 


6,496 


8 


4 


4 


3 


.29 


4.1 


5,521 





1 















a In Tables VII and IX the designation "not emerged" is used for those stages and adults which have 
not left the cells in which they developed. Adults which have previously left the cells within which 
they matured and have subsequently sought shelter within any i)art of "the bolls are designated as 
"emerged." 

Besides showing that large numbers of weevils entered hibernation 
in or upon tliese bolls, this table shows that bolls do not provide 
sufficient shelter to insure the survival of hibernating weevils in a 
winter so severe as was that of 1904-5. 



SHELTER DURING HIBERNATION. 



27 



Table VIII. — C'limatic conditions at Dallas, Calvert, 
ami at Keatckie, La., December 1, 1904, to March 31, 
talitij of weevils hibernating in bolls. 



Palestine, and Victoria, Tex., 
1905, producing complete vmr- 



UECEMBKU, 1904. 





Temperature. 


Rainfall. 


Locality. 


Time.s 
below 
32° F. 


Absolute 
mini- 
mum. 


Average 
mini- 
mum. 


Monthly 
mean. 


Depar- 
ture from 
iionnal. 


Depth. 


Depar- 
ture from 
normal. 


Dallas, Tex 


1.5 
6 

14 
,5 
5 


°F. 

20 
22 
21 
22 
30 


"F. 

33.1 

39.4 

37.6 

40.1 

44.1 


"F. 
40. G 
48.9 
50.0 
49.6 
54.8 


°F. 

- 1.2 

- . 5 
-1- .1 

- 1.8 

- 3.0 


Inches. 
0.74 
9.62 
2.58 
4.08 
1. 59 


Inches. 
-1.40 
-1-4.94 


Calvert, Tex. b 


- .04 

4- .27 




— .20 








9 




38.8 


50.0 


- 1.3 


3.70 


+ .702 









JANUARY, 1905. 



Dallas, Tex 

Keatchie, La. «. 
(Calvert, Tex. b. . 
Palestine, Tex . . 
Victoria, Tex. . . 

Average. . 

Dallas, Tex 

Keatchie, La. i. 
Calvert, Tex. 6. . 
Palestine, Tex.. 
Victoria, Tex. . . 

Average . . 



24 


12 


27.8 


38.7 


- 6.2 


3. 05 


12 


17 


33.6 


■ 41.0 


-4.9 


4.13 


13 


IC) 


34.1 


44.8 


- 3.1 


2.01 


11 


18 


34.7 


43.0 


- 2.8 


2.06 


6 


25 


43.1 


5.3.0 


— .6 


3.84 


13 




34. 60 


44.1 


- 3. .52 


3.02 



-fO. 33 

- .47 

- .44 
-2.25 
-f 1.41 



.284 



FEBRUARY, 1905. 



30 


2 


24.6 


35.2 


- 9.4 


2.81 


19 


(i 


31.4 


39.4 


-11.8 


4.12 


21 


10 


28.2 


39.2 


-10.7 


3.02 


21 


6 


31.9 


40.0 


-11.0 


2.47 


10 


20 


34.7 


44.1 


- 9.9 


3. 62 


20 


8.8 


30.2 


39.6 


-10.6 


3.21 



-fl.ll 

- .04 

-1-1.20 
-1.00 
-t-1.42 



-I- .59 



MARCH, 1905. 



Dallas, Tex... 
Keatchie, La. a 
Calvert, Tex. h. 
Palestine, Tex. 
Victoria, Tex.. 

Average . 






35 


47.1 


59. 6 


+ 4.0 


4. 44 





42 


53.5 


62. 6 


-f- 5.0 


5. 03 





35 


51.6 


62.1 


+ 4.4 


4. 95 





37 


53.7 


62.4 


-f- 2.5 


3.95 





46 


57.2 


65.8 


-1- 3.1 


5. 04 







52.6 


62.5 


+ 3.8 


4.68 



+ 1.29 
+ .39 
+ 2.34 
+ .14 
+ 3.52 



+ 1.54 



o Temperatures for Shreveport, I^a. 



t> Temperatures for Ilearne, Tex. 



An examination of tliis tal)le shows that the temperature went below 
freezing with remarkable frequency during this period. The most 
severe cold weather occurred during February, w hen the temperature 
averaged 10 degrees or more below normal throughout the State of 
Texas. The absolute minimum for this season at the five points 
mentioned is recorded by the Weather Bureau as being 2 degrees 
above zero at Dallas. At Calvert the minimum temperature was 10 
degrees and at Victoria 20 degrees. In most of the localities there 
was an excess of rainfall, so that the winter as a whole may be 
characterized as having been unusually cold and wet. 



28 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



While tlicse records show that few if any weevils survived in the 
slielter of bolls during this season it must be remembered that the 
weevils were not exterminated in all of these localities. Other con- 
ditions of shelter were evidently so much more favorable than bolls 
as to have enabled the weevils to survive this severe venter. It is 
true, however, that in the spring of 1905 weevils occurred in much 
smaller numbers than is usually the case. 

Other examinations of bolls show that in the northern portion of 
the infested area of Texas there is a smaller percentage of living stages 
in the bolls than in the southern portion. The data for three seasons 
are compared in Table IX. The periods selected are during the 
last of the winter season in each year. 

Table IX. — Increase in percentage of survival in bolls from northern to southern Texas. 





March, 1904. 


■February and March, 1905. 




Bolls 
exam- 
ined. 


Stages alive. 


Bolls 
having 
living 
forms. 


Living 
forms. 


Bolls 
exam- 
med. 


Stages alive. 


Bolls 

having 
living 
fonns. 




Section. 


8J 


ft 


Adults. 




Adults. 


Living 
forms. 




s 


a 


si 

h5 


8J 
P 


^a 

0) 


T3 

o 
to 

s 

a 

w 


Northern 

Central 


2, (100 

ISO 


















1 


Per ct. 


0. .55 


Per ct. 



3,258 
4., 575 


4 



4 



1 



4 
4 




14 
11 


Per ct. 

0.27 

.00 

.24 

1.80 


Per ct. 

0. 026 
.000 


Southern 2.50 


2.3 ■ 2S 




9, .589 i 4 1 1 
S09 1 i 

1 


.096 








.833 














February and March, 1900. 


Total. 




Bolls 

exam- 
ined. 


Stages alive. 


Bolls 

having 
living 
forms. 


Living 
forms. 


Bolls 

exam- 
ined. 




Section. 




ft 

3 


Adi 

o t* 


ilts. 

■d 
be 

i 


Stages 
found 
alive. 




6,186 
6,650 
1,410 












1 

5 

1 


2 
11 
10 


Per ct. 

0.04 

.24 

.78 


Per ct. 





12,044 

11,405 

11,249 

809 


12 


Central 


17 


Southern 


85 


Brownsville 


15 





















It is noticeable that there is a gradual increase in the living stages 
from north to south, and that toward the end of the hibernation period 
nearly all of the living stages are adults, most of which had matured 
before the beginning of hibernation. 

That the increased mortality found in bolls during the winter of 
1904-5 can not be attributed entirely to the exceptional severity of 
that season is shown by the fact that a similar decrease in the per- 



SHELTER DURING HIBERNATION, 



29 



centage of living stages was found in examinations during January 
and February of 190G. In January among 1,933 bolls examined in 
several localities 86 adults and stages were found. In February 
14,246 bolls were examined and only 30 adults were found. The 
lowest temperature experienced during January was 12° F. at Dallas, 
with the mean temperature of 49.6° F. in an average of the eight locali- 
ties where the examinations were made. During February the abso- 
lute minimum was 15° F. at Dallas and the average minimum 38.5° F. 
During these two months in the localities where examinations were 
made the minimum temperature went below 32 degrees on an aver- 
age of only nineteen days. 

Table X. — ('limati.c comlUian.s ai ciylit pointii in Texas, January to Manli, 1906. 

JANUARY. 





Temperature. 


Precip 


tat ion. 


Locality. 


Times 
below 
32" F. 


Absolute 
mini- 
mum. 


Average 
mini- 
mum. 


Monthly 
mean. 


Depar- 
ture from 
normal. 


Depth. 


Depar- 
ture from 
normal. 


Dallas 


IS 
12 
15 
10 
11 
Hi 
3 
3 


12 
19 
21 
21 
22 
19 
2() 
25 


30.8 
35.4 
36. 6 
39.2 
36.0 
34.9 
41.6 
42.1 


"F. 
44.4 
48. (■) 
49.9 
49. 6 
51.2 
47.4 
51.4 
54 4 


°F. 
-0.5 
-hi. 7 
-f2.0 
-t-3..S 
+3.1 
— . 8 
+ 2.7 
+ .8 


Inches. 
1.98 
1.97 

.81 
1.92 
1.38 
4.85 

.81 
1.34 


Inches. 
-U. 74 






Ileanie ... . 


— 1.65 


Palestine 

Waco 

Nacogdoches 


-2.39 

— . 55 
+ 2.11 
-1.(.7 




— 1.09 








11 




37.1 


49. 6 


+ 1.6 


1.S8 


- .83 








FEBRUARY. 


Dallas.. 


12 
9 
7 
7 
8 

10 
G 
5 


15 ' 32.6 
19 1 37.1 
23 1 37.2 
22 38. 7 


46.0 
58.0 
49.4 
48.6 
50.8 
48.2 
52.1 
54.4 


+ 1.4 
+ 1.9 

- .5 
-2.4 

- .8 

- .4 

- .6 
+ .4 


2.23 

2.61 
4.22 
3.06 
2.65 
1.73 
1.29 
2.01 


+ 0. 53 


Corsicaiia 


+ .49 




+ 2.40 


Palestine 


- .45 


Waco 

Nacogdoches 

Austin 


20 
20 
2(i 

28 


37.3 
36. 7 
43.9 
44.3 


+ .72 
-2.09 
- .59 
+ .19 






Average. . 


8 




38.5 


51.0 


— .12 


2.4S 


+ . 15 












MARCH. 










Dallas 


11 
5 
2 
2 
3 
3 
1 
1 


25 

27 
26 
28 
27 
27 
32 
31 


38.9 
39.7 
43.4 
44.1 
43.2 
44.0 
47.8 
50.5 


50.8 
49.9 
55.4 
53.4 
57.5 
54.3 
56.8 
61.0 


-4.8 
-7.6 
-2.3 
-4.2 
-1.1 


3.24 
2.10 
1.97 
1.24 
2.95 
1.63 
2.47 
2.24 


+ 09 




— 1.25 




64 


Palesti ne . . . 


_o 74 


Waco 


— 09 




—2. 82 


Austin 

Victoria 


+ .25 

+ .72 


Average 


3. .3 


44. 


55.0 


-3.54 


2.23 


- .94 



A comparison of the principal points shown in Tables VIII and 
X indicates the relative severity of the two seasons, especially in 
the columns showing absolute minimiun and average minimum 



30 HIBERNATION OF THE COTTON BOLL WEEVIL, 

temperatures aiul departures from normal. The records for February 
are especially significant. In 1905 this month was unusually cold 
throughout the State. The absolute minimum for the five local- 
ities considered in that year was 2 ° F. at Dallas and the average mini- 
mum was 8.3° F. below that occurring in 1906. In 1905 the mean 
average temperature for the month was 10.6° F. below the normal 
while in 1906 it was but 0.12° F. below normal. It was during this 
month of (extreme cold with excessive rainfall in 1905 that the great- 
est mortality among weevil stages occurred. 

HIBERNATION SHELTER OTHER THAN BOLLS WITHIN THE FIELD. 

During an ordinary season it can not be doubted that a large 
majority of the weevils which survive find some other shelter than 
the bolls hanging upon the plants. It is not, however, as easy a 
matter to find weevils in rubbish scattered upon the ground as in 
bolls. It is necessary to collect the rubbish very carefully and sift 
it over cloth or paper to separate the weevils from the trash. In 
this way it has been found that weevils hibernate extensiveh^ in the 
leaf and grass rubbish distributed throughout the field. Naturally 
the cleaner the field in the fall the smaller will be their chances of 
finding favorable shelter during the winter. 

Standing trees are a common sight in cotton fields, and while the 
records of weevils found hibernating imder bark are but few they 
are suflicient to indicate that these trees may be a rather important 
factor where they occur in considerable numbers. Where the 
vSpanish moss (Tillandsia usneoides) (PI. II, fig. 1) occurs, as in the 
bottom lands in the coast section of Texas and in the southern por- 
tions of the Gulf States, weevils find exceptionally favorable shelter 
within this moss. On January IS j\Ir. J. I). jNIitchell cut down a 
moss-covered tree growing in a large cotton field in the vicinity of 
Victoria, Tex. Between 400 and 500 jjounds of moss growing on 
this tree was collected and examined very carefully. Tlu-ee living 
specimens of the boll weevil were found. On February 5, 1907, a 
similar experiment was tried. One thousand poimds of moss was 
obtained from a tree standing in the midst of cotton fields. The 
moss was situated from 7 to 15 feet above the ground. Among a 
large number of other insects found hibernating in the moss there 
were ten living boll weevils. The weevils seem to prefer the festoons 
of green hanging moss to the bunches of dead matted moss (PL II. 
fig. 2). 

The turnrows and ditches throughout the fields and the fence rows 
(PI. I, fig. 2) surroimding them present exceptionally favorable con- 
ditions for successful hibernation. It has been noticed frequently 
that early in the season the most severe injury ma}^ occur on the 
edge of a field adjoining a fence row where weeds and grass abound. 



j|. 77, Bureau of Entomology, U. S. Dept. of Agncultuie. 



Plate I. 




Weather-Recording Apparatus and Fence-Row Shelter. 

Fig. ].— Wfalht.T apparatus used in recordiiiK tomperatiiri.' and humidity conditions. Fig. 
Tyiiical weedy fence row, atTording excellent shelter for weevils. (( )ri,i,'inal. ) 



Bui. 77, Bureau of Entomology, U, S. Dept, of Agriculture. 



Plate II. 




Favorable Shelter Conditions in and around Fields. 

Fig. 1. — Cotton Held adjoining grove of trees laden witli Sjianisli moss ( Til/dinhin iisindidi ■■<). 
Fig. 2. — Near view of moss. Fig. 3. — Cotton stiilli liaving many liolls inlesied 1j\ wei'vils 
at hibernation lime. (Original.) 



SHELTER DURING HIBERNATION. 31 

One fact should be emphasized in regard to practically all classes 
of shelter which liave been mentioned as occiuTing within cotton 
fields, i. e., that it is possible as a ride to destroy or remove practi- 
cally all of them. Undoubtedly the burning of cotton stalks, weeds, 
grass, and other rubbish is the easiest and most effective method of 
destruction where it can be practiced. Next to this in importance 
woidd be the destructi(jn of the stalks by a stalk chopper and plowing 
inider all the rubbish. In the latter case it must be stated that 
many weevils which may be buried to an average depth of 2 inches 
will be able to escape through the soil and may then find shelter 
around, if not within, the field. 

HIBERXATION SHELTER Ol TSIDE OF COTTOX FIELDS. 

Unquestionably timber fringes skirting cotton fields are exceed- 
ingly important because of the shelter which the fallen leaves and 
undergrowtli provide for weevils during the winter. The conditions 
to be found here are so exceedingly favorable that a majority of 
})Ianters seem to recognize that the most severe infestation of young 
cotton in the spring may be expected to occur near such timber. 
Where the moss (PI. II, fig. 1) occurs abundantly it is second onl}^ 
in importance to the fallen leaves as a shelter for weevils. The fact 
that weevils have been taken early in the spring upon trees at a dis- 
tance as great as 2 miles from a cotton field shows the extent to 
which they ma}' possibl}' scatter during the fall or seek for cotton 
during the spring. The planter need not, however, be alarmed by 
these facts, inasmuch as it is certain that but few weevils hiber- 
nating away from the immediate vicinity of cotton fields will sur- 
vive to find food supply upon emergence. 

Cornfields adjoining cotton or cornstalks scattered throughout 
cotton fields may shelter many weevils. This was fu'st noticed by 
i\Ir. E. A. Schwarz at Victoria in the winter of 1901-2 and has since 
been corroborated by a number of observers. Several examina- 
tions have been made of haystacks in the vicinity of cotton. This 
is a task quite comparable with that of seeking for the proverbial 
needle and it is not surprising that the residts have been very meager. 
The fact, however, that traces of weevils have been foinid in these 
examinations indicates that weevils may find shelter under such 
conditions. 

Farmyards, seed houses, barns, ginneries, and oil mills also aft'ord 
exceptionally favorable shelter for weevils. Especially in ginneries 
and seed houses (PI. Ill, fig. 1) the weevils become concentrated 
with the concentration of the cotton or seed and frequently may be 
found in large numbers within or around these buildings. In con- 
nection with this subject the reader is referred to a fuller discus- 



32 



HIBEENATION OF THE COTTON BOLL WEEVIL. 



sioii of the significance of ginneries and oil mills in the distribution 
of weevils and of the methods recommended for controlling them 
which may be found in Farmers' Bulletin No. 209 of the Department 
of Agriculture, ''Controlling the Cotton Boll Weevil in Cotton Seed 
and at Ginneries." Numerous observations have shown that weevils 
have been taken into new localities through the agency of shipments 
of cotton seed and cotton-seed hulls from ginneries and oil mills 
handling infested stock. Definite observations have been made 
showing that living weevils may occur in cotton seed at planting 
time. While it is probable that few would survive in a large mass 
of seed it is certain that some might do so and be distributed in 
the planting of the seed. 

Table XI .—Experiments of 1904 to 1906 to test hibernation in cotton seed. 



Locality. 


When 
put in 
hiberna- 
tion. 


Weevils 
put in 

hiberna- 
tion. 


When 

exam- 
ined. 


Weevils 
found 
alive. 


\\'eevils 
found 
dead. 


Terrell, Tex 


1904. 
Nov. 13 
Nov. 30 
Dee. 15 
Nov. 14 
Nov. 15 
Nov. .30 
Dec. 15 
Nov. 10 
Nov. 17 
Nov. 25 
Dec. 1 
Dee. 8 
Dec. 15 


200 
200 
250 
150 
200 
200 
200 
200 
200 
200 
200 
200 
200 


1905. 
Apr. 20 
Apr. 21 
Apr. 22 
Apr. 19 
Apr. 7 
Apr. 8 

...do 

Apr. 3 

...do 

Apr. 1 
Mar. 31 
Mar. 29 
Mar. 28 













1 
1 


154 


Do 


139 


Do 


170 


Corsicana, Tex 


127 


Calvert, Tex 


152 


Do . . 


176 


Do 


142 


Victoria, Tex 


130 


Do 


144 


Do 


150 


Do 


115 


Do 


149 


Do 


123 






Total 


2,600 


a2 


1,871 




1905. 
Nov. 1 
Nov. 18 
Dec. 4 
Dec. 15 


1906. 
Apr. 28 
Apr. 30 
May 3 
May 4 


Dallas, Tex 

1)0 

Do 

Do 


100 
200 
200 
900 








92 
160 
181 
862 






Total 


1,400 





1,295 




Nov. 7 
do 


Apr. 2 
Apr. 7 
Apr. 3 

...do 

Apr. 5 




Victoria, Tex 


100 
100 
100 
100 
100 









93 


Do 


93 


Do 

Do 

Do 


Nov. 13 
Nov. 80 
Dec. 11 


97 
100 
96 


Total 


500 





479 









o On .January 27 47 dead and 18 living weevils were removed, and on March 4 4 dead and 1 living weevils 
were removed. 

While the number and percentage of weevils surviving in these 
experiments is very small indeed, the fact that some do survive is the 
special [loint having significance. The occasional occurrence up to 
])lanting time of living weevils among seed from infested locahties 
is alone sufficient justification for every quarantine restriction which 
has been placed upon cotton seed and other cotton products by 
uninfested territory. 

The Mexican entomologist Prof. L. de la Barreda, under the direc- 
tion of Prof. A. L. Herrera, of the Comision de Parasitologia Agricola, 



HIBERNATION EXPEEIMENTS IN SMALL CAGES. 33 

has made some very pertinent observations on the occurrence of 
boU weevils in cotton seed intended for planting. " In January, 1903, 
this entomologist examined a number of sacks of seed received from 
the infested area of Texas for planting in the Laguna region in Mexico. 
Six sacks from one consignment were selected. In these, 12 living 
weevils were found, together with 56 dead ones. Later examinations 
were made of a number of shipments of seed from the infest(Hl por- 
tions of the United States. In every case living weevils were found. 
This work was done in the montli of January. These observations 
show clearly the real danger that exists in the shipment of cotton 
seed from infested localities to those where the weevil does not occur. 

HIBERNATION EXPERIMENTS IN SMALL CAGES. 

In many ways it is possible to obtain more accin-ate data upon 
hibernation of weevils through cage experiments than through field 
observations. In the cages conditions may be prepared which are 
typical of those to be found in the fields. The number of weevils 
within a given space can be largely increased without overcrowding, 
so far as the possibility of their finding shelter is concerned. The 
action of the weevils in seeking and in leaving shelter can be deter- 
mined more accurately in cages than in the field. The food condi- 
tions may be varied to represent various field conditions and, finally, 
knowing definitely the number of weevils placed under certain con- 
ditions, it is possible to follow them closely enough to determine with 
a great deal of accuracy the proportions surviving. From a com- 
parison of the results obtained under various experimental condi- 
tions those conditions which are most favorable as well as those which 
are least favorable to successful hibernation may be determined with 
considerable certainty. In all of our experimental work of this nature 
the cage results have been checked so far as has been possible by 
field observations. 

With the continued study of the boll-weevil problem the necessity 
for increasingly comprehensive experiments upon hibernation has 
become apparent. The work thus shows from year to year a growth 
m complexity with the constant purpose of increasing the accuracy 
of results by making the experimental conditions conform as closely 
as is possible to field conditions. In the early stages of the work the 
hibernation cages were small and portable. Some were placed out 
of doors where they would be fully exposed to prevailing climatic 
conditions; others were placed in the shelter of buildings or under 
similar conditions where the favorable nature of the shelter provided 
might be determined. 

a Boletin de la Comision de Parasitologia Agricola, vol. 2, No. 2, pp. 45 to 61. 
90317— Bull. 77—09 3 



34 HIBERNATION OF THE COTTON BOLL WEEVIL. 

CAGE EXPERIMENTS OF 1902-3. 

In the experiments made during the season of 1902-3 most of the 
weevils used were collected in the field at Victoria, Tex., about the 
middle of December. Some, however, were reared weevils which 
during the months of September and October previous had become 
adult. They were confined in boxes and jars covered with cheese 
cloth. Various kinds of rubbish were placed in the cages, some of 
which were placed in the fields and some in a building. 

These cages were all examined between April 15 and 30, 1903. 
Among the 25 lots tested, including 356 weevils, it was found that 
an average of about 1 1 per cent had survived. None of those which 
were adult before November 1 was living on April 15, while nearly 
16 per cent of those taken in the field about the middle of December 
were still alive on April 27. A slightly higher percentage had sur- 
vived in the inside tests, and it appears that a considerable degree 
of dryness favored survival. One-half of all the weevils surviving 
were found in the folds of dead banana leaves on April 15, while the 
balance were scattered among hay, dried cotton leaves, empty bolls, 
and in or under earth. 

CAGE EXPERIMENTS OF 1903-4. 

During the season of 1903-4 450 weevils were tested in lots of 
about 50 each. From October 21 to December 16 one or more lots 
were started each week, part of them being placed outdoors and 
part indoors. In addition to the confinement of adults, about 400 
infested sc{uares were picked from the ground about November 15 
and kept until the following ^larch. These scjuares were examined 
on March 18. It was found that most of the stages had perished 
while yet larva?. Nearly one-fifth of the squares contained dead 
adults. In the lot among 128 stages there was one adult which was 
still alive. 

Examination in April, 1904, accounted for all but 15 of the 450 
weevils confined, but one weevil was found ahve, and that one was 
placed in hibernation on October 29 in a cage out of doors. The 
results during this season seem to contradict in some respects those 
obtained during the preceding year, which indicated the favorable 
nature of inside shelter. 

CAGE EXPERIMENTS OF 1904-5. 

The work of the season of 1904-5 was planned to include a number 
of localities representing in a general way the various portions of the 
weevil-infested area. In all cases the cages consisted of boxes about 
1 by 2 feet in size and covered with 14-mesh galvanized-wire screen- 



HIBEKNATION EXPERIMENTS IN SMALL CAGES. 



35 



ing. These were all placed out of doors at various dates between 
November 3 and December 15, 1904. The examinations were made 
during April, 1905. 

Table XII. — Summary of hibernation experimeiits, 1904-5. 





s 

a . 
■-^ a 

1 


■6 
g 


q3 

C 

1 


Total number of weevils found— 


Locality. 


Is 
Si 


g 
o 

a 
o 


•6 
a 

I 

a 


i 

§ 

a 
a 


o 

1 

1— ( 


a 


a 

g 

o 

a 


a 

o 

o 

a 


<D 
> 

i 

o 

d 


o 
+J 
o 
o . 

O m 

£! 


1 
P. 
a 


t 
a 

"> 
p 

"S 
o 
ft 
cl 
O 


Terrell Tex 


715 
650 
489 
572 
500 
900 


244 

254 
229 
278 
240 
601 








11 


108 
116 
120 
1G7 
84 
190 


68 
58 
68 
60 
47 
190 


13 
14 
10 
23 
45 
6 


1 




3 

8 



7 




28 
23 



6 
8 
4 
21 
15 




Paris, Tex 


3 
24 


5 
3 
5 


19 




Keitliville La 






2 
11 




Calvert, Tex . . 


"gi" 


24 






12 








48 


12 


















Total 


3,826 


1,846 


11 


785 


491 


111 


92 


35 


7 


51 


54 


75 


25 


32 


12 







The most striking point shown in this table is the fact that no 
weevils survived except at Victoria. Even there the percentage was 
very small. Undoubtedly from 5 to 10 per cent of the weevils placed 
in the cages must have escaped through the wire before the season 
became cold enough for all to hibernate. The explanation for the 
death of all weevils confined north of Victoria, Tex., may be found 
in the exceptionally severe climatic conditions occurring during this 
season. These have already been indicated in Table VIII, page 27. 
It should be stated, however, that while weevils were scarce in the 
spring of 1905 in all of these localities they were not exterminated 
in Texas except at Paris. At this place examinations made during 
the season of 1905 failed to show any weevils in a field which had 
been quite heavily infested late in the season of 1904. 

HIBERNATION EXPERIMENTS IN SMALL CAGES, 1905-6. 

Tests were made at Dallas, Calvert, and Victoria, Tex., representing 
the northern, central, and southern sections of the infested area. 
Owing to the increased complexity of the experiments and the more 
valuable character of the results obtained, it seems advisable to 
present the data in a somewhat more detailed manner. 



36 



HIBEKNATION OF THE COTTON BOLL WEEVIL. 



Table XIII. — Suininury of hibernation experiments in boxes ut Dallas, Calvert, and 
Victoria, Tex., in 1905-6. 



DALLAS. 



When 
put in. 


Kind of rubbish. 


Out- 
doors 
or in- 
doors. 


Wee- 
vils 
put 
in. 


When ex- 
amined. 


Number of wee- 
vils found- 
Alive. Dead. 


Per- 
centage 
alive. 


Remarks. 


1905. 
Nov. 1 

Do... 
Do. . . 


Com shucks, grass, 
cotton leaves. 

Cotton leaves 

do 


Out. . . 

In 

In 

In 

Out... 

In 

In 

Out... 

In 

In 

Out... 

In 

In 

/Out... 
iln 


100 

100 
100 
100 
100 
100 
200 
200 
200 
200 
200 
200 
900 


1906. 
Apr. 27 

...do 

...do 

Apr. 28 
Feb. 19 

...do 

Apr. 30 
May 1 

...do 

May 3 

...do 

May 1 
May 4 







3 










92 

SO 

64 

92 

82 

87 

160 

165 

165 

181 

140 

195 

862 







1 











In chicken house. 


Do... 

Nov. 17 

Do... 


Saclf of cotton seed... 
Grass, leaves, rubbish . 
do 


Do. 
Do 


Nov. 18 


Cotton seed . . 


Do 


Nov. 26 

Do... 

Dec. 4 


Only grass 

Grass, seed, cotton. . . 
Cotton seed 


Do. 


Dec. 11 
Do... 


Corn shucks, leaves . . 
. do 




Dec. 15 


Cotton seed 


300 in each of 3 sacks. 




Total 






600 
2, 100 


3 



479 
1,886 


0.5 
0.0 























CALVERT. 



1905. 
Nov. 7 

Do .. 


Com shucks, grass, 
cotton, 
do 


In 

Out... 

In 

Out... 

/Out. . . 
\In 


100 

94 
205 
200 

294 
305 


Nov. 27 
Do... 


do 

do 




Total 







1906. 
Apr 18 

...do.... 
...do.... 
Apr. 19 



45 
205 
145 



190 
303 



14.0 
0.0 



VICTORIA. 



1905. 
Nov. 5 
Nov. 7 

Do... 
Nov. 13 

Do... 
Nov. 30 

Do... 
Dec. 11 

Do... 



Mixed 

do 

do 

do 

do 

do 

do 

do 

do 



Total. 



Total of 3 local- 
ities 



Out... 
Out... 

In 

Out... 

In 

Out... 

In 

Out... 
In 

/Out... 
tin 

/Out. . . 
\In 


100 
100 
100 
100 
100 
100 
100 
100 
112 


1906. 
Apr- 6 
Apr. 7 

...do 

Apr. 4 
Apr. 5 

...do 

...do 

Apr. 7 

...do 


2 
1 

4 

1 

3 
4 


43 
23 
73 
53 
97 
39 
94 
51 
100 


2 
1 

4 

1 

3 
3.57 


500 
412 


11 

4 


209 
364 


2.2 ■ 
!97 




1,394 

2,817 


55 
4 


878 
2,553 


3.9 
.14 







In the small-cage experiments of 1905-6 but three localities were 
tested. In the 26 experiments were placed 4,211 weevils, of wdiich 
number 1,394 were out of doors and 2,817 indoors. In only one 
cage did weevils survive within doors, and that was at Victoria, 
where it would seem that such protection was least needed. The 
two most striking results were the small survival at Dallas and the 
remarkably large survival in one of the outdoor experiments at 
Calvert. In the outdoor tests an average of 3.9 per cent survived, 



HIBERNATION EXPERIMENTS IN SMALL CAGES. 



37 



while in the others but 0.14 per cent survived. Tn an averao;e of 
all tests the survival was 1.4 i)er cent. 

The nature of the shelter failed to show any si.si;ni(icant influence 
in these small-cage experiments. 

The relative favorableness of outside conditions is shown in the 
following; table by a com])arison of the data in each of the three 
localities. This table does not include the experiments with cotton 
seed: 

Table XIV. — Comparison of siirviral irrords outdoors and indoors for Dine IV.ras 

localities in T.)05-C>. 





Outside. 


Inside. 


Locality. 


Weevils 
put in 

lnl)erna- 
tiou. 


Weevils survived. 


Weevils 

put in 

hiberna- 

tion- 


Weevils survived. 




Numlier. 


Percent- 
age. 


Number. 


Percent- 
age. 




500 
294 
GOO 


11 

41 

3 


2.2 


412 


4 




0.97 


Calvert, Tex 


14.0 1 305 
.5 2,100 





Dallas, Tex 









Total 


1,394 


55 


3.9 2.817 


4 0.14 













During this season it is very evident that in all localities outdoor 
conditions were decidedly more favorable for successful hibernation. 
Upon the average the survival out of doors was twenty-eight times 
as successful as in the tests made indoors. 

Grouping the experiments accortling to fifteen-day periods from 
November 1 to December 15, when they were instituted, the most 
favorable time for entering hibernation seems to be indicated. 

Table XV. — Comparative favorableness of periods for entering h.ibernation, 1905. 





Period. 


Total 
survival. 




Nov. 1-15, 1905. 


Nov. 1.5-30, 1905. 


Dec. 1-15, 190.5. 


Num- 
ber. 




Locality. 


Weevils 
put in 


Weevils 
survived. 


Weevils 
Weevils survived. 

put in ! 


Weevils 
put in 
hiber- 
nation. 


Weevils 
survived. 


Per 

cent. 




hilier- 
nation. 


Num- 
ber. 


Per 
cent. 


hiber- 
nation. 


Num- 
ber. 


Per 
cent. 


Niun- 
l)er. 


Per 
cent. 






500 
194 
300 


7 
1 



1.4 

.5 
.0 


200 
405 
COO 


1 
40 
3 


0.5 

10.0 

.5 


212 


7 


3.3 


15 
41 
3 


1.00 




0. so 


Dallas, Tex 


400 








.23 








Total 


994 8 


.8 


1,205 


44 


3.7 


C12 


7 


1.1 


59 


2.10 











This table does not include the experiments in cotton seed. The 
com])arisons show that during the fall of 1005, November 15 to 30 
was more favorable than either an eai'lier or later ])erio(l at Calvert 



38 



HIBERNATION OF THE COTTON P.OLI. WEEVIL. 



and Dallas, while at Victoria the ])oii()il between December 1 and 15 
was more favorable. 

The shelter conditions within which weevils survived was also 
determined in these experiments, and the principal i)oints are shown 
in the following table, which again does not include cotton-seed tests: 

Table XVI. — Shelter in ivJiich siirviviiig ivccvih vere found in April and May, I'JOd. 



]vOcaIity. 


Bermuda 

grass and 

hay. 


Excelsior. 


1 'aper. 


Banana 
leaves. 


Corn 
shucks, old 

cotton 
stalks, and 

bolls. 


Total. 


Victoria, Tex 


5 


4 


1 


1 


4 
41 


15 


Calvert, Tex 


41 


Dallas, Tex 


3 








3 














Total 


8 


4 


1 


1 


45 


59 







This shows the favorable nature of old corn and cotton stalks, 
among which the survival in one cage at Calvert was surprisingly 
large. It also indicates that weevils may survive in varied shelter, 
and that in all probability the temperature and moisture conditions 
exj^erienced may be as important as the nature of the shelter in 
determining survival. 

LARGE-CAGE EXPERIMENTS, KEATCHIE, LA., 1905-6. 

With the work of 1905-6 a change was made in the method of 
carrying on the hibernation experiments. Instead of using numer- 
ous small boxes in a number of places, large screen-covered cages were 
utilized in the fields at Keatchie, La., and Dallas, Tex. The Keatchie 
cage (PL III, fig. 2) was constructed under the direction of Mr. 
Wilmon Newell, secretary of the State crop pest commission of 
Louisiana and special field agent, cooperating in the boll weevil 
investigations. It was probably the largest structure of its kind 
that has ever been built for an entomological investigation. The 
interior was divided by partitions into eighteen sections. The 
shelter conditions for the weevils and the dates upon which weevils 
were inclosed were planned to represent the extremes of field condi- 
tions as to shelter and date of entrance into hibernation. The gen- 
eral })lan of the experiment is shown in the first section of Table 
XVII, and in the last section are included the emergence records for 
the cage. 

Before entering \\\^oi\ a discussion of the work at Keatchie special 
credit should be given Mr. Wilmon Newell and his assistant, Mr. J. B, 
Garrett, who were particularly concerned in the execution of the 
work at Keatchie. Much work has also been done by Mr. W. D. 
Hunter upon the reports of the Keatchie experiments in arranging 
the data so as to show the most significant facts. 



Bui. 77. Bureau of Entomology, U. S. Dept. of Agriculture. 



Plate II!. 





Seed H> 



Hli 1 i;\. 



Gai,e, Keatchie, La. 



FiK. l.-S, 
19U.") 



1 liduse <i|iiMisitr uiiich the lirst si.mi nf ueovil work was found at Keatchio, La., in 
Fig. 2.— Lari;e cage liuilt for hibi'inatioii experiments in 1905-ti. (Original.) 



LAEGE-CAGE EXPERIMENTS, KEATCHIE, LA., 1905-G. 39 

Table XVII. — Suvimary of installalion and emergence records in cage at Keatchic, Lu. 



Installation records, 1905. 


Emergence records, 1900. 


1 

a 

O 

o 


Where weevils 
were collected. 




3 '•' 
Z 


I'^holfer in cage section. 


March. 


April. 


May 1-14. 


Z 


1 

2 
1 
5 

2 
2 
2 


1 

4 
9 
1 

4 



c 
o 

u 


z 


a 
§ 

o 

Ah 


z 


■a 

a 

u 
u 

Ph 


1.. 

2. 
.3 


Louisiana. 

...do 

...do 


Nov. 29 

Nov. 25 
...do.... 


1,200 

1,000 
1,000 

1,000 
1,000 
1, 000 

2,100 
1,500 
1,000 
1,000 
1,000 
1,000 
1,000 

4,000 
4,000 
1,000 
1,000 
1,000 


Brush, leaves, moss, stumps, logs; 

stalks removed. 

Same, but stalks standing 

Cotton seed piled; plants left 

standing. 

Same, liut seed left uncovered 

Absolutely bare 


0. IGG 
....... 

.2 
.1 

.5 

.09 

.14 
_ 2 
.2 

....... 

.1 
.22 
.1 
.4 


3 

7 
4 

5 
1 
IS 

17 
33 

9 
15 
10 
17 

2 

29 
94 
15 
17 
15 


0. 25 

. 7 
.4 

.5 
.1 
1.8 

.81 
2.2 

.9 
1.5 
1.0 
1.7 

. 72 
2^35 
1.5 
1.7 
1.5 


4 

10 




4 

16 
15 
3 

4 
12 
1 

17 
28 

5 
10 

8 


0.33 
1.0 


4.. 


...do 

...do 


...do 

...do .... 




(i 


Te.xas 

...do 

...do 

...do 


Nov. 23 

Nov. 29 
Nov. 25 
...do 


Ordinary field . 


4 


7 


Stalks, grass, etc.: 

Same as 1 


7G 


8 


Same as 2 


1 


9 


Same as 3 


3 


10 


...do 

...do 

...do 

Louisiana. 

Texas 

...do 

...do 

Louisiana. 
...do 

Totals and 


...do 

...do 

Nov. 23 
Dec. IS 

Dec. 3 

...do 

Dec. 8 

Nov. 28 
Nov. 18 


Same as 4 




11 


Same as 5 


. 4 


n 


Same as (i 


1 2 


13.. 

14.. 

15 


Stalks left; leaves, etc., added; 
shaded. 

Same as 13, but not shaded 

Same as 14 


.1 

.42 


1(i 


do 




17 


do 


1 


18.. 


Check on 13: stalks, grass, leaves, 
not shaded. 


.8 




averages. 25, SOO. 


38 


.18 


311 


1.2 


137 


.53 









Installation records, 1905. 


Kmergence i 

March 1 to 
May 14. 


-ecords 

u 

A' 
o 


Total per cent of \ § 
survival. .~ 


il 


1 

3 

o 
■n 


Where weevils 
were collected. 


on 

?! 


i 

o ti 

z 


Shelter in cage section. 


o o 


z 




c3 a 


1.. 

2 
3^; 

4.. 


Louisiana. 

...do 

...do 

...do 

...do 

Texas 

...do 

...do 

...do 

...do 

...do 

...do 

Louisiana. 

Texas 

...do 

...do 

Louisiana. 
...do 

Totals and 


Nov. 29 

Nov. 25 
...do 

...do 

...do 

Nov. 23 

Nov. 29 
Nov. 25 

...do 

...do 

...do 

Nov. 23 
Dee. 18 

Dec. 3 

...do 

Dec. 8 

Nov. 28 
Nov. 18 

averages. 


1,200 

1,000 
1,000 

1,000 
1,000 
1,000 

2, 100 
1,500 
1,000 
1,000 
1,000 
1,000 
1,000 

4,000 
4,000 
1,000 
1,000 
1,000 


Brush, leaves, moss, stumps, 

logs; stalks removed. 

Same, but stalks standing 

Cotton seed piled; plants left 

standing. 
Same, but seed left uncovered. 
.■\bsolutelv bare 


9 

17 
5 

7 
2 
27 

35 
50 
14 
17 
14 
29 
4 

50 
132 
21 
31 
23 

487 


0.75 

L7 
.5 

.7 

.2 

2.7 

.06 
3.33 
1.4 
1.7 
1.4 
2.9 

.4 

1.25 

3.3 

2.1 

3.1 

2.3 


26 

25 
6 

8 
4 

38 

44 
64 
17 
22 
26 
55 
8 

86 
170 
35 
41 
53 


2.16 

2.5 
.6 

.8 

.4 

3.8 

2.09 
4.26 
1.7 
2.2 
2.6 
5.5 
.8 

2.15 

4.25 

3.5 

4.1 

5.3 


11 

9 
16 

15 
17 


t) 


Ordinary field 


6 


7. . 


Stalks, grass, etc. : 
Same as 1... 


13 


8 


Same as 2 


3 


9 


Same as 3 


14 


10 


Same as 4 


10 


11 


Same as 5 


8 


1'> 


Same as 6... 


1 


13.. 

14.. 
15 


Stalks left; leaves, etc., added; 
shaded. 

Same as 13, but not shaded 

Same as 14 


15 

12 
4 


in 


do 


7 


17 


do 


5 


18.. 


Check on 13; stalks, grass, 
leaves, not shaded. 


2 




25,800 


L5 


728 


2.82 











40 TTTBERNATION OF THE COTTON BOLL WEEVIL. 

The beginning of this work occurred so hite in November that none 
of flie sections can be considered as having been phiced in hiberna- 
tion early. Cold weather occurred between about November 30 and 
December 3, during which time the majority of weevils entered 
hibernation. Emergence appears to have begun on ]\farch 22, and 
the last weevils emerged on June 28. The emergence during April 
and May was quite uniform, while duriiig June it decreased rather 
steadily. In these records no allowance has been made for the escape 
of weevils through the wire on the cage. Using the number placed 
in the cage (25,800) as a basis, the 728 weevils which emerged con- 
stitute a survival of 2.82 per cent. It is impossible to call attention 
to all of the many interesting points shown in this table. Special 
emphasis, however, will be given several points through the rear- 
rangement of the significant data in succeeding tables. 

Since climatic conditions are primarily responsible for hiberna- 
tion and the emergence of weevils therefrom, the records shoidd 
be studied in relation to a chart of the temperature conditions, 
such as is given in figure 1. No climatic records are available for 
Keatchie previous to the beginning of these observations upon March 
15. The emergence of weevils may well be shown in relation to the 
range in temperature upon the same chart. In studying the effects 
of temperature variations upon weevil activity it has been found 
that those temperatures which are about 43° F. alone produce activity 
among the weevils. Because of this fact 43° F. is regarded as the 
starting point in emergence records, and all temperatures above 43 
degrees may be spoken of as "effective temperatures" upon the 
following diagram ; the average between the maximum and minimum 
extremes for the day is recorded as the mean average temperature. 
While it is probably true that maximum temperatures have a special 
significance in their effect upon emergence from hibernation, and that 
minimum temperatures have a special effect upon entrance into 
hibernation, it will be more simple and sufficient in this study to use 
the single line representing mean average temperature during the 
emergence period. 

From this diagram it will be seen that the emergence at Keatchie 
in 1906 occurred practically during four rather clearly defined periods. 
These periods are separated b}^ marked declines in the mean average 
temperature. It will be noticed that as it became warmer following 
these cold periods there was an increased emergence of the weevils. 
After the middle of May so large a proportion of the living weevils 
had emerged that the number recorded became gradually smaller, 
although the temperature rose still higher. 

Some of the special facts demanding attention are those relating 
to the effect of the various conditions of shelter upon the survival 
of weevils, the relation of emergence to effective temperature in 



LARGE-OAOE EXPERTMENTi^, KEATriTTE, LA., l'.)0r)-6. 



41 



various periods, the 
to the time of enier<r( 



rehition of the time of putting; into hibernation 
nee therefrom, the rehition of aecunuihiied effect- 





ff/^ IN FALL IN INCHES 

a § i S ^ 


























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3 












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RAlkfALt /N ?NCHES 



!^ MEAN /iVERA<SE TEMP£ffATUffE,D£6fi£ES FAHffENHE/r 
■n tn ouioinouiomooiS 






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A/UMBER or WEEV/LS £M£FiGED 



ive temperatures to emergence, and the longevit}^ of the emerged 
weevils. These subjects will be considered under succeeding topics. 

FAVORABLE CONDITIONS FOR HIBERNATION. 

For a stud}" of favora])le conditions for hi])ernation those s(H'tions 
have been selected which are most strictly com])ara])le in respect to 



42 



HIBEKNATION OP THE COTTON BOLL WEEVIL. 



the time weevils were ])l;iced therein, the source of the weevils, and 
the nature of the shelter. Practically one-half of the weevils used 
were collected in Texas and sent to Keatchie for this work. The 
sections used in this comparison received weevils between Novem- 
ber 23 and 29. 

Tahlr XVIIL — Favorable conditions for Jiibcrnation determined by rank in percentage 
oftveevils surviving at Keatchie, La., in 19().'>-6. 



Section nuiu- 
l)er in cage. 



6 and 12 

2 and 8. 
1 and 7. 

4 and 10 

5 and 11 

3 and 9. , 



Nature of shelter. 



Ordinary field stallis, grass, etc 

Brush, leaves, stumps, logs; stalks standing. . . 

Same as above, but stalks removed 

Cotton seed, piled but uncovered; stalks stand- 
ing 

Absolutely bare ground 

Cotton seed piled and covered ; stalks left stand- 
ing 





Weevils 


survived. 


Weevils 
put in. 




Number. 


Per cent. 


2,000 
2,500 
3,300 


93 
99 
70 


4.65 
3.50 
2. 12 


2.000 
2,000 


30 
30 


1.50 
l.,50 


2,000 


23 


1.15 



Kank of 
section. 



It is evident that ordinary fiekl conditions where stalks are allowed 
to stand together with the grass and leaves littered over the ground 
are as favorable for successful hibernation as any conditions. It must 
be admitted that the shelter conditions in the bare sections (5 and 11) 
are not such as would occur in a field plowed in the fall because of the 
fact that the inclosed weevils could still find shelter in the structure of 
the cage itself. This will undoubtedly explain the survival of 1.5 per 
cent in two sections having no rubbish on the ground. It is apparent, 
however, that even with this advantage of cage structure over bare 
ground, slightly more than three times this percentage of weevils sur- 
vived where ordinary field conditions existed. Without the shelter 
afforded l)y the cage this difference would undoubtedly be very much 
greater. In 9 sections which contained rubbish, among 15,500 wee- 
vils, 567, or 3.66 per cent, survived. The shelter may therefore be 
held accountable for increasing the survival at least 2.1 per cent. 
Thus upon an area where no more than 15 weevils might survive with- 
out protection, 36 at least might be expected to survive with the pro- 
tection. 



EFFECT OF ACCLIMATIZATION UPON SURVIVAL AND EMERGENCE. 

It has already been mentioned that about one-half of the weevils 
used in this work were collected in Texas and one-half at Keatchie, La. 
In order to determine whether this difference in the geographical sec- 
tion in which the weevils developed might exert an influence upon 
their survival and emergence the records for a number of comparable 
sections are combined. These weevils were all j)laced in hibernation 
between November 25 and 29, 1905. 



LARGE-CAGE EXPERIMENTS, KEATCHIE, LA., 1005-0. 



43 



Table XIX. — Comparison of emergence records at Kentchie, La., for vrcrils roUrdcd 
in Louisiana with those collected in Texas. 





Date. 


Pereentago of enior- 
geuce during eaeli 
month ba,s('il upon 
total eniers^onee of — 




f.,200 wco- 
vils col- 
loclPd in 

Louisiana. 


(l.OOO wee- 
vils col- 
leeted in 
Texas. 




1900. 


9.09 
33.63 
21.82\rn 
28. \sr' 

7.2.H 


4.0 


April 


4S.0 


May 1-14 


4.0 


May 15-June 1 . . . 


June 2-30 










100.00 


100.0 



Altogether in these sections 110 of tlie Louisiana weevils and 178 of 
the Texas weevils emeri2:e(l, making; a })ercentao:e of total survival in 
the former case of 1.77 and in the latter case of 2.62. On the whole 
the Texas weevils emero:ed slightly earliei' than did those collected in 
Louisiana, hut the records are too nearly similar to indicate that such 
would reo-ularlv be the case. 



RELATION OF EMERGENCE TO EFFECTIVE TEMPERATURES. 

The practical point in these studies of tem})erature an<l emergence 
relationshi})s is to ascertain the facts upon which emergence depends, 
so that it may be possible from a study of tem])erature records for any 
localit}^ to form fairly relialde conclusions as to the effects which those 
temperature conditions may have had upon weevil activity. In this 
way it may be possible to determine approximately the time when 
weevil emergence begins, the time when the majority of weevils will 
probably have left their hibernation quarters, and approximately the 
time at which emergence becomes complete. In this connection it 
will be profitable to compare the records for Dallas, Tex., with those 
for Keatchie, La., for the same periods. 

The total effective temperature is obtained by computing the sum 
of the mean average effective temperatures for each of the days 
included within the period shown. For exain])le, if the mean average 
temperature for the first day of a period is 60° and for the second day 
68°, the average effective temperature for the two days is 17° and 25°, 
respectively. The sum of these, or 42°, is the total effective temper- 
ature for those two dates. 



44 



IIIBERNATTON OF THE COTTON BOLL WEEVIL. 



Tahlk XX. — Relation of rjfrrtivc temperatures to ewergenee at Keatchie, La., and 

Dallas, Tex., luoc. 



Periods of emerKenec. 



Mar. 15-21 

Mar. 22-27 

Mar. 28- Apr. 2. 

Apr. 3-13 

Apr. 14-20 

Apr. 21-Mav 5. 

May 6-13 

May 14-23 

May 24-29 

May 30- June 11 
June 12-30 



Total ellective 
temperature. 



Keatchie. Dallas. 



"F. 

12.0 
141.0 

37.0 
275.5 
118.5 
484.7 
176.0 
339.0 
201.0 
413.0 
667. 



"F. 

5.5 
151.8 
66.6 
243.6 
124.1 
435.8 
159.8 
300.2 
196.8 
478.0 
700.0 



Average effective 
temperature. 



Keatchie. Dallas 



op 

1.7 
23.5 

7.4 
25.0 
16.9 
32.3 
22.0 
33.9 
33.5 
37.5 
39.2 



"F. 

0. 78 
25.3 
11.1 
22. 14 
17.7 
29. 
19.9 
30.0 
32.8 



Number of weevils 
emerging. 



Keatchie. Dallas. 



12 
165 

28 
187 

49 
173 

23 

65 
7 



An examination of this table shows three very distinct periods of 
emergence, the first being from April 3 to 13, inclusive; the second 
from April 21 to May 5, inclusive; and the third from May 14 to 23. 
No weevils emerged from the Dallas cages after ]\Iay 23. At Keatchie 
a fourth period may be considered as occurring between May 30 and 
June 11. In this place the emergence ceased on June 28. It is 
noticeable that between June 20 and 27 no weevils had emerged. 
It will be noticed in the table that the periods of largest emergence 
are separated by periods having decidedly lower temperatures, 
during which emergence was decreased, although it did not cease 
entirely. 

The relation of emergence to 5-degree increments in effective tem- 
perature is shown in Table XXI. 



Table XXI. 



■Tlic relation of enierejence to increase in effective temperature at Keatchie, 
La., and Dallas, Tex., 1906. 





Keatchie, La. 


Dallas 


, Tex. 






Range of 
ellective 










Total num- 
ber of 


Per cent, 
based on 






tempera- 


Number of 


Per cent of 


Number of 


Per cent of 


weevils 


grand total 


tures. 


weevils 


total 


weevils 


total 


emerged. 


emerged. 




emergmg. 


emergence. 


emergmg. 


emergence. 






1-14°.... 


20 


2.7 








20 


2.5 


15-20°.... 


52 


7.1 


o 


3.6 


54 


6.8 


21-25°.... 


116 


16.0 


25 


45. 5 


141 


17.8 


26-30°.... 


127 


17.5 


IS 


32.7 


145 


18.5 


31-35°.... 


309 


42.4 


10 


18.2 


319 


40.7 


36-40°.... 


84 


11.5 








84 


10.7 


41-50°.... 
Total. 


20 


2.7 








20 


2.5 


728 


100.0 




100.0 


783 


100.0 



The number of weevils emerging under 14 degrees of effective 
temperature, or 57° F., is very small indeed. From that point the 
emergence increases with the increase in temperature until after a 
majority of the weevils have emerged. Most weevils left their 
winter quarters during an effective temperature averaging between 



LARGE-CAGE EXPERIMENTS, KEATCHIE, LA,, 1'J05-IJ. 



45 



21 and 35 degrees. At Keatchie 75 i)er cent and at Dallas 96 per cent 
of the total emergence took place between these limits. At Dallas 
the largest emergence occurred between 21 and 25 tlegrees of effective 
temperature, while at Keatchie the largest emergence occurred 
between 31 and 35 degrees. 

In considering the effect of temperature upon emergence it must be 
remembered that the nature of the shelter within which the weevil 
hibernates must inevitably have an important bearing on the time at 
which the weevil becomes active. 



KELATIOX OF TIME OB^ ENTRANCE INTO HIBERNATION TO SURVIVAL 

AND EMERGENCE. 

It has previousl}" been stated that none of these experiments was 
instituted more than about a week before it became cold enough for 
practically all w^eevils to hibernate. For this comparison it is pos- 
sible to use only the data for those sections having similar conditions 
as to (1) the source from which weevils were obtained, (2) the time 
when they were placed in the cage, and (3) the general nature of the 
shelter afforded. 

Table XXII. — Relation of time of cineryence in 1906 to time of sfurtiny hibernation 

in 1905. 



Section 

number in 

cage. 



7 and 8 

14, 15, and 
16. 

17 

18 



When wee- 
vils were 
put in. 


Percentage of total 


emergence 


, 1906, occurring in— 


Percent 
of sur- 
vival. 


March. 


April. 


M^yi-^^- K?: 


June 2-30. 


Nov. 25 
and 29. 

Dec. 3 and 
8. 

Nov. 28... 

Nov. 18... 


3.7 

4.8 

9.7 



46.3 

47.4 

41.4 
28.3 


28.7 
17.1 

24.4 

15.0 


15.7 

24.7 

22.0 
32.0 


5.5 
5.5 

2.4 

24.5 


3.0 

3.23 

4.1 
5.3 



Remarks. 



Texas weevils. 
'Louisiana weeviLs. 



In the first section of the table, among weevils collected in Texas, 
it is apparent that there was practically no difference in the time of 
emergence between those placed in hibernation from November 25 
to 29 antl those started December 3 to 8. In the second part of the 
table, among the Ijouisiana weevils, those entering hibernation 
Noveinber 18 emerged more slowly than did those ])laced in the cage 
November 28. The explanation of this may probably be found in 
the fact that the first date w-as not sufficiently early to insure the 
death of many weevils by starvation before they could hibernate. 
It did, however, allow a larger proportion of them to penetrate deeply 
into the shelter than in the case of weevils placed in the cage ten days 
later, which was onl}" one day before a marked decrease in tempera- 
ture. The weevils placed in the cage on December 3 and 8 experi- 
enced warmer temperatures than those placetl in on the 28th of 
November, and, therefore, found conditions more favorable for their 



46 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



entrance into hibernation. The records indicate that there is a most 
favorable time for entrance during which weevils may find shelter 
from which they will emerge rather later than the average during the 
following spring. 

THE RELATIONSHIP OF ACCUMULATED EFFECTIVE TEMPERATURE TO 

EMERGENCE. 

In studying the relationship of accumulated effective temperature 
to emergence the hiitial point has been set arbitrarily at February 1. 
It would be both interesting and profitable if we could determine 
])ositively the exact effective temperature conditions under which 
emergence from hil)ernation begins. This point will be further dis- 
cussed in the light of the additional records obtained in Texas in 1907. 

The object in this particular study is to determine the relation 
of accumulated effective temperature to the accumulation in emer- 
gence. The records for both Keatchie and Dallas are included for the 
sake of comparison. 

Table XXIII. — Relation of accunnilatcd cj'cctirf tcinpcraturc to the bc(ji)ming and 
accumulation of emergence, Keatchie, La., and Dallas, Tex. 



Periods of emergence. 


Accumulated ef- 
fective tempera- 
ture. 


Accumulated nuin- 
lier of weevils 
emerged. 


Accumulated per- 
centage of total 
emergence. 




Keatchie. 


Dallas. 


Keatchie. 


Dallas. 


Keatchie. 


Dallas. 


1900. 
Feb. 28 


"F. 

145. (i 

282. 1 

294.1 

435. 1 

472.1 

747. (i 

80G. 1 

1,350.8 

1,520.8 

1,805.8 

2,000.8 

2,479.8 

3,140.8 


"F. 

208. (1 

325. 

330.5 

482.3 

548. 9 

792. 5 

910. (1 

1,.302.4 

1.512.2 

1,812.4 

2,009.2 

2,487.0 

3,188.0 







25 
37 
202 
230 
417 
40(i 
039 
002 

734 


[: 


2 

30 
30 
48 
48 
55 
55 
55 
55 








.3.4 

5.0 

27.5 

31.3 

50.8 

03.4 

87. 

90.0 

99.0 

100. 





Mar. 1-14 





Mar. 15-21 





Mar. 22-27 


3.0 


Mar. 28-Apr. 2 . 


3.6 


Apr 3 13 


54.5 


Apr. 14-20 


54.5 


Apr. 21-Mav 5 . 


87.2 


Mav ()-13 


87.2 


Mav 14 23 


100.0 


Mav 24 29 




Mav 30-.Tiine 11 




June 12-30 









Emergence at Dallas became complete with the accumulation of 
slightly over 1,800 degrees of ett'ectivo temperature, while at Keatchie 
complete emergence required slightly over 3,000 degrees of effect- 
ive temperature. At Dallas 87 per cent of weevils had emerged 
when 1,512 degrees of effective temperature had accumulated and 
the same percentage had emerged at Keatchie with 1 ,865 degrees 
effective temperature. For the last 13 per cent of weevils emerging 
but 300 degrees of temperature accumulated at Dallas, while at 
Keatchie nearly 1,300 degrees accumulated. It is probable that at 
Dallas during this season the emergence in the cage was completed 
somewhat sooner than would have been the case normally, on account 
of the late period of starting the experiments. 



LARGE-CAGE EXPERIMENTS, KEATCHIE^ LA., 1905-6. 



47 



At Victoria in the spring of 1904 the period of emergence from 
hibernation was determined in the fiekl under exceptionally favor- 
able conditions. A severe drought, occurring immediately after 
most of the cotton had been planted, so retarded germination that 
the sprout cotton developed nearly two months in advance of 
the planted. Large numbers of weevils emerged before most of the 
planted cotton was through the ground. Practically the only food 
supply afforded these weevils was found in the sprout cotton. By 
reducing the num])er of sprout plants upon a field of 65 acres it was 
possible to examine at frequent intervals all of the plants. Since 
all weevils found at each examination were collected and removed 
from the field those found at the next subsequent examination may 
be considered as having emerged in the interval. The development 
of squares upon the most advanced plants was not suilicient to 
make it possible for any weevils of the first generation to have become 
adults before June 1. The collections from the sprout plants were 
continued until May 26, and it is probable that some weevils emerged 
from hibernation after this date. Our knowledge of the weevils at that 
time was not such as to enable us to distinguish accurately between 
hibernated- and recently emerged adults after that date. For that 
reason May 26 was considered as representing the conclusion of 
emergence from hibernation, although it probably continued longer. 



Table XXIV. 



-Relation of accumulated cj/'ectivc tciupcraturc to accumulated einenjence 
in. Jicld observations at Victoria, Tex., in 1904- 



Fel). 1-2S 

Mar. 1-lS 

Mar. 19-25 

Mar. 20-31 

Apr. 1-5 

Apr. (M2 

Apr. 1.3-16 

Apr. 17-May 1 
May 2-11.."... 

MaV 12-19 

May 20-2(3 



Accumu- 
lated 
etleetive 
tempera- 
ture. 



F. 

508. 
5S5. 5 
,117.5 
,240.0 
,37S.5 
,5,37.0 
, CiSfi. 
, 104. 
..374.0 
,.W4. 
,.S14. 5 



Accumu- 
lated 
mmiber 
of plants 
of cotton 
sprouts 
examined. 



None. 
250 
650 
1,190 
1,720 
2,120 
2,320 
2,570 
2,990 
4,163 
5,900 



Accumu- 
lated 
percentage 

of plants 
examined 

to entire 

nmnber 
exanuned. 



None. 
4.2 
11.0 
20.1 
29.1 
3.5.9 
39.3 
43.5 
50. 6 
70.5 
100. 



Accumu- 
lated 

lunnher of 
weevils 
found. 



None. 
19 
39 

65 
100 
160 
200 
224 
376 
521 
648 



Accumu- 
lated 
percentage 
of weevils 
at each date 
to entire 
number 
found. 



None 
2.93 
6.01 

10. oa 

15.40 
24. 60 
30. «C 
34.50 

58. OC 

81. or 

100. 00 



A comparison of Tables XXIII and XXIV shows that there was a 
much grejiter accumulation of temperature at Victoria for the same 
percentage of emergence than occurred at either Dallas or Keatchie, 
although the Keatchie record appears to exceed the Victoria record 
in the amount of accumulated temperature accompanying complete 
emergence. It seems very probable that in the field records the 
accumulations are excessive because of two facts; first, at each 



48 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



examination all weevils were considered as emerging upon the date 
of the examination, whereas in the cages the weevils were collected 
daily. The second reason is that upon plants in the field there was 
a much greater possibility of overlooking weevils which were present 
and which might be found and counted as having emerged upon 
some succeeding examinations. Table XXIV is, however, of value 
in supporting the records given in Table XXIII, especially because 
similarly favorable conditions for determining the full period of 
emergence in the field may rarely occur. 

LONGEVITY OF WEEVILS AFTER EMERGENCE IN KEATCHIE EXPERI- 
MENTS. 

For determining longevity after emergence the weevils emerging 
during short periods were placed together in a smaller cage provided 
with a variety of rubbish but with no food. Examinations of the 
small cages were made at frequent intervals and the period between 
the average date when weevils were placed in the cage and the aver- 
age date of examinations was recorded. The figures are arranged 
chronologically according to emergence. 

Table XXV. — Lomjcvity of weevils after cmcryenee from Inbernation, without food, at 

Kcatchic, La., 1DU6. 



Date of eniergoiice. 



March 2ti. 
April 10.. 
April 11.. 
April 12.. 
April 13.. 
April 14.. 
April I.S.. 
April 16.. 
April 17.. 
April 19.. 
April 20. . 
April 21.. 
April 22.. 
April 23.. 
April 24.. 
April 25.. 
April 20.. 
April 28.. 
April 30.. 
May 1.-.. 

May 2 

May 4 

Ma-v 5 



Nuinlier 
of weevils 
emerged. 



Weevil - 
days, a 



62.0 
905 ^ 
751.0 
078. 5 
261.0 
169. 
100. 5 

59.0 



55. 

119.0 

92.0 

378.5 

132.5 

36.0 

83.5 

24.0 

855. 

313. 

15. 

173.0 

431.0 

342.0 



Average 

munl)er 

of days 

lived. 



62. 
21.7 
21.4 
23.4 
32.6 
24.1 
20.1 
29.5 



10.8 
10.2 

k;. 4 

22.0 

9.0 

9,2 

8.0 

18.5 

17.3 

7.5 

11.5 

15.3 

18.0 



Date of eiuergeiice. 



1906. 

May 7 

May 8 

May 10 

May 11 

May 12 

May 13 

May 14 

May 15 

May 16 

May 17 

May 18 

May 22 

May 23 

May 25 

May 28 

May 29 

May 30 

Juiie 9 

June 19 

Totals and 

average . . . 



Nunilier 
of weevils 
emerged . 



Weevil- 
days. ti 



292. 5 

262. 

1.0 

54.5 

13.0 

1.5 

58. 5 

26.0 

169. 5 

58.0 

48.5 

23.5 

29.0 

26.5 

1.5 

7.5 

35.0 

7.0 

4.0 



7,155.0 



Average 

nuniljer 

of days 

lived. 



IS. 2 

16.3 

1.0 

9.0 

3.2 

1.5 

7.3 

13.0 

13.0 

9,6 

12.1 

11.7 

14.5 

13.2 

1.5 

7.5 

8.7 

7.0 

4.0 



17.11 



"In the third column of the table the expression "weevil-days" is used to signify the total number of 
days lived by the total number of weevils recorded for a certain date. For examjile, if one weevil had 
lived 10 days, a second 15 days, and a third 23 days the total number of weevil-days for these 3 individuals 
would be 48 and the average number of days lived would be 16. 

It is noticeable that weevils emerging early in the season survived 
far longer than the average period, while those emerging toward the 
end of the season survived for less than the average period. For 
the 418 weevils tested the average duration of life without food 
proved to be slightly over seventeen days. 



LAEGE-CAGE EXPERIMENTS AT DALLAS, TEX., 1905-6. 



49 



LARGE-CAGE EXPERIMENTS AT DALLAS, TEX., 1905-6. 

The work at Dallas for 1905-6 was planned especially to check 
the results of the experiments at Keatchie which have been described. 
The cage used (PI. IV, fig. 1) was divided into four sections, each 
having a ground area of 100 square feet. In one section the natural 
conditions of shelter were left unchanged (PL IV, fig. 2). There 
was practically no grass upon the ground, but the growth of stalks 
was quite heavy. In the other three sections the shelter provided 
(PI. V, figs. 1 and 2) for the weevils was arranged in such a way 
that it might be possible to divide each section into two parts by a 
middle partition. Unfortunately the first cold weather occurred 
before the weevils could be placed in these sections, and it was neces- 
sary to keep the weevils confined in boxes for several days until it 
became sufficiently warm to render them active so that they might 
find shelter in the cages. The weevils were liberated at approxi- 
mately the center of each section and allowed to move in any direc- 
tion they might choose. The object of this was to determine whether 
particularly favorable rubbish might exert a special attraction for 
the weevils. 

About three weeks after the weevils were liberated an examina- 
tion was made of each section and the number of weevils crawling 
actively upon the wire was determined. An examination of the 
boxes from which the weevils were liberated and which had been 
left undisturbed in the cages during this period showed that a large 
mortality had occurred before the weevils really entered hibernation. 
Table XXVI shows the principal points in regard to the beginning 
of the experiments and the emergence of the weevils during the 
following spring. 

Table XXVI. — Lurgc-cayc cxpcrimcnls in hibernation at Dallas, Tec, I'Mo-G. 



Section 
of cage. 


Kind of shelter. 


Weevils 
put in. 


Active 
weevils, 
Decem- 

lier 20, 
1905. 


Weevils 
found 
dead, 

Decem- 
ber 26, 
1905. 


Percent- 
age of 
weevils 
active, 
Decem- 
ber, 1905. 


Percent- 
age of 
living 
among 
those ex- 
amined. 


Date of 

fu-st 
emer- 
gence, 

1900. 


Day of 

largest 
emer- 
gence, 
1900. 


I 


Cotton stalks 

Cotton stalks re- 
moved March 
22, 190(). 

Cotton stalks and 
leaves. 

Bare 

Uav. 


2,ti00 
2,500 


375 

200 


G15 
515 


14.4 

8.0 


3,s.0 
2,s. 


Apr. 4 
Mar. 22 

Apr. 4 

Apr. 23 
May 14 

Apr. 4 
Apr. 9 


May 2 
Apr. 9 

Apr. 11 

Apr. 23 
May 14 

Apr. 11 
Apr. 9 


II: 

I't. 1... 

I't. 2... 


Ill: 

rt. 1... 

Pt. 2... 


2,500 


2(;0 1,205 


10. 4 


17.7 


IV: 

I't. 1 . . . 
I't. 2... 


Piled l)0xes 

Corn and cotton 
stalks. 

Total and 
average. 


2,500 


2;?S 1,025 


9.5 


12.7 














10,100 


1,073 


3,900 


10.0 


21 k 





90317— BulL 77—09- 



50 HIBERNATION OF THE COTTON BOLL WEEVIL. 

Table XXVI. — Large-cage experiments in hibernation at Dallas, Tex., 1905-6 — Con. 





Kind of shelter. 


Emergence l)y periods. 


Total 
sur- 
vival. 


Per- 
cent- 
age 
of 

sur- 
vival. 


Rank 
of 


Section 
of cage. 


Mar. 
22-31. 


Apr. 
1-10. 


Apr. 
11-20. 


Apr. 
21-30. 


May 
1-10. 


May 
11-20. 


Mav 
21-31. 


cages 

on 
basis 
ofsur- 
vival. 


I 






2 










1 
3 
G 

1 



4 
2 


2 


7 




3 



4 
3 
3 

1 



2 



4 



1 








2 



1 


1 

1 




U 






2 



13 

8 

18 

2 
1 

12 

2 


0.5 
1.04 

.12 
.56 


2 


11: 

Pt. 1... 

I't. 2... 
Ill: 

Pt. 1 


Cotton stalks removed 

March 22, 190(i. 
Cotton stallis and leaves. . . 

Bare 


4 
1 
5 


Pt. 2... 


Hay 


7 


IV: 

Pt. 1 


Piled boxes 


3 


Pt. 2... 


Corn and cotton sialics 

Total and average. . . 


6 




2 


17 


12 


13 


5] 5 


2 


56 


.5 





The division of sections 2, 8, and 4 was made by inserting a par- 
tition of cheese cloth early in the spring of 1906 before any weevils 
became active. The i)erceiitage of survival has been based upon 
the total number of weevils placed in the four sections. It should 
be borne in mind that the conditions at the time of entrance into 
hibernation were decidedly unfavorable for the weevils, as is shown 
in the fact that about 35 per cent had died before December 26 and 
under such conditions as to indicate that they were very weak at the 
time they were placed in the cage. No allowance has been made for 
the escape of weevils through the wire. It thus appears that approxi- 
mately 1 per cent of the weevils which really may be said to have 
entered hibernation survived and emerged between March 21 and 
May 31. The survival in the bare section was less than one-fourth 
of the smallest survival in the sections provided with rubbish. For 
the sake of comparison with the records at Keatchie, La., some data 
from the Dallas ex})eriments have been used in connection with 
those at Keatchie in several of the tables which have already been 
given. 

NATURE OF WEEVIL ACTIVITY- FOLLOWINO EMERGENCE FROM HIBER- 
NATION. 

In following tiie activity of enierged weevils it was deemed advis- 
able to pursue a very different method at Dallas from that which 
has been described at Keatchie. Instead of removing weevils from 
the sections in which they had emerged, each weevil was marked in 
such a way as to make it possible to recognize it individually and the 
weevils were allowed to remain practically undisturbed in the sec- 
tion where they had spent the winter. In making the daily exam- 
inations record was kept of the appearance or disai)})earance of each 
individual weevil. No food was suj)j)lied in any of the sections until 



Bui, 77, Bureau of Entomology, U. S. Dept. of Agriculture. 



Plate IV. 




Hibernation Experiments, Dallas, Tex., 1905-6. 

Fig. 1. — Four-section cage nseii for experiments, built over cotton. Fig. 2. — .Shelter <-(.)n(litions as 
occurring naturally in sectitm 1. (Original.) 



Bui. 77, Bureau of Entomology, U. S, Dept, of Agriculture. 



Plate V. 




Shelter Conditions in Dallas, Tex., Experiments, 1905-6. 

Fijj;- 1.— Piled ruttdu ^lalks ami pilcil lioxt-s in scctidii 2. Fi,;;. L'.— Standing,' cdtlun .■^talks vor.sus 
jiilfd lfa\-i.'s, .-cciidn A. (OT\g\]\ii\.) 



LARGE-CAGE EXPERIMENTS AT DALLAS, TEX., 1905-6. 



51 



towaixl the close of the experiments m May, when seed was i)hinte<i 
and cotton began growing before the last weevils emerged. Some 
very interesting results were obtained from this method of observa- 
tion. A majority of the weevils were seen a second time, and some 
disappeared and reappeared as many as eight times. The longest 
period between the first and second appearances of any individual 
was forty-three days. 

Table XX\ll.—Intermillcvt activity of unfed iveerdls after emergence, at Dallas, Tex., 

1906. 







Number of weevils 








Weevils "rehibeniated" — 


a 






























Once. 


Twice. 


Three times. 


II 




















t^ 






— - . 
































5fi 
















P o 


a 


9 


0) 

s 

0) 


<D 




0) 


S 

a 


0) 

a 




, 




>> 


B 


P. 




a 
O 


H 




o 


s 




CO 


3 


;z; 


p 


:z; 




iS 


ft 


-^ 


46 


26 


15 


11 


6 


2 


2 


1 


17 


8.7 


6 


7.2 


2 3.5 


G.8 



As has been previously shown, entrance into hibernation is a 
gradual process and weevils which have first become quiet may sub- 
sequently become active and seek other shelter before finally hiber- 
nating. In a very similar way emergence from hibernation is 
gradual but extended throughout a longer period of time than is 
entrance into hibernation. The observations recorded in Table 
XXVII also show conclusively that weevils may leave their winter 
quarters during warm days and, failing to find food, they may agahi 
become quiet and emerge again after a considerable interval. This 
fact has an important bearing upon the proposition which is fre- 
quently advanced by planters of starving the weevils in the spring 
by deferring the time of planting. While many weevils might i)erish 
in this way, it is certain that many more woidd be able to survive 
and reappear at intervals, so that there would be plenty of weevils 
to infest the crop, even though this might be i)lanted as late as is 
possible to secure any yield. 

Other observations were made upon the intermittent activity of 
unfed w^eevils during the spring of 1906. Weevils from Calvert, 
Victoria, and Brenham, Tex., were tested. The weevils from Cal- 
vert and Victoria, Tex., had been confijied in hibernation cages 
throughout the winter. Those from Brenham were collected in the 
field early in March. None of these weevils had tasted food after 
emergence. In tliese tables the date of death, unless otherwise indi- 
cated, is considered as having Ijeen tlie middle date between the last 
examination at which a weevil was found alive and that at which it 
was found dead. 



52 HIBERNATION OF THE COTTON BOLL WEEVIL. 

Table XXVIII. — Inter mittent activity of unfed emerged weevils, I'JOG. 



Locality. 



Calvert, Tex. . 
Victoria, Tex. 

Brenham, Tex 



When 
collected. 



1905 

Nov. 25 

/Nov. 7,13 

\Dec. 11 

1900 
Nov. 1 



When 
put in hi- 
bernation. 



1905 
Nov. 27 
Nov. 7,13 
Dec. 11 



When 
removed 
from hi- 
bernation. 



190(1 
Apr. 19 

►Apr. 



Mar. 



When 
rehil)er- 
nated. 



1906 
Apr. 23 

Apr. 10 
Mar. 7 



Weevils 
put in rehi- 
bernation. 



Date of 
first ex- 
amina- 
tion. 



May 10 
Apr. 24 

May 11 



Locality. 



Calvert, Tex... 
Victoria, Tex. . 
Brenham, Tex 



Weevils 
surviv- 
ing. 



Date of 
second 
exami- 
nation. 



May 22 
Mav 10 
May 23 



Weevils 

surviv- 



Date of 
third 

exami- 
nation. 



Juno 8 
May "si 



Weevils 
surviv- 
ing. 



Date of 
death of 
longest 
survival. 



June 8 
May 10 
May 31 



Average 
length of 
life in 
rehiber- 
nation. 



Days. 
30.4 
19.1 

07.4 



The records for Calvert and Brenham show a very remarkable 
power of endurance in some weevils, the average survival for the 
two lots of 20 and 8 weevils being over thirty and sixty days, 
respectively. 

CLIMATIC CONDITIONS PRODUCING EMERGENCE FROM HIBERNATION 
AT DALLAS, TEX., IN 1906. 

In the figure given below, representing climatic conditions and 
the emergence at various dates, the temi)erature line given repre- 
sents only the mean average effective temperature. 

In this case, as at Keatchie, the emergence occurred especially dur- 
ing four w^ell-defmed periods and the conclusions stated in connection 
wath figure 1 ap})ly equally well to the results shown in figure 2. 

EMERGENCE IN THE FIELD AT VICTORIA, TEX., IN 1906. 

The observations iq^on emergence in the field at Victoria, Tex., 
ill 1906, were begun too late in the spring to indicate the limits of 
the first i)art of the period of emergence. For this work a field of 
about one-half acre was selected in wdiich it was apparent early in 
May that there would be a large number of hibernated adults. The 
observations were planned to furnish information particularly upon 
two points under field conditions: (1) The determination of the 
period of emergence and (2) the period of activity of emerged wee- 
vils. The w^ork was done by Mr. A. C. Morgan, who devoted par- 
ticular attention to a study of this field throughout the season of 
1906. The nielliod followcnl w^as to examine every i)laiit and every 
square or boll throughout this area. After the first tw^o examina- 



EMERGENCE IN THE FIELD AT VICTORIA, TEX., IN lOOfi. 



58 



tions had been inado it became apparent that some method must be 
adopted to eiial)le the weevils found at eaeli examination to be (hs- 
tingiiisliecL At each subsequent examination, therefore, the wee- 
vils found were marked witli a ])aint of a different color. Early in 
the season the weevils emerging from hibernation were sufhciently 
numerous to practically prevent the setting of fruit upon this area. 
The first w^eevils of a new generation did not begin to appear until 



q;90 

1 

5 50 
43»F 


MAIRCH 
5 fO 15 20 25 


S 10 15 20 25 


S 10 15 20 25 


1 

i 

'^ 

li 

1 








































































/ 












h 
















A 










J 












I 






\ 






f 


\r 


A 




W 


\f^ 




















r 






f 


V 






\ 


/ 















r 






4^ 


h 




th 


L 






y 


/ 






\ 


1 






i 












V 








If 










\\ 


\ 


\A 


i 


]i 




f 


1 
































\) 


\r 


\ 




m 




r 












1 




] 
















11 












' $ 














1 
















II 












































V 


T 






























< •» 








V 































3.50 

r 

$2.00 
51.50 
^1.00 






































3.50 
3 00 03 
250| 

200^ 

150^ 

1.00 1 

050 


























































































■ 


















































-- 


























I 










I 








1 




J 












/ 










":i 


f 




r. 




1 


1 


I 




r 






/ 








// 








Fig. 2.— Chart showing mean average temperature, rainfall, and weevil emergence, Dallas, Tex., March 

to May, 1906. 

about June 20. It w^as then easily possible to chstinguish between 
hibernated adults and those wdiich were not more than two or three 
weeks old. It is probable that the oil paints which were used may 
have been responsible for the death of many of the weevils marked, 
since it was liardly possible in the field to apply the paints with the 
necessarv care. 



54 HIBERNATION OF THE COTTON BOLL WEEVIL. 

Table XXIX. — Emergence records for onc-half-acre field at Virtorki, Ter., /!)()(!. 





Number of weevils found. 




Datt> of(>x:uiiina- 
lion. 


■6 

a 

d 
1^ 


<•< 




-d 

0) 


Ed 
s a 
a d 

^ o 


Remarks. 


1900. 
May 10 


340 

358 

492 
220 
105 
731 


,-f 


9 


•f 


9 


d 


? 


34C> 
358 

492 
355 
228 
739 


Weevils not removed. 
















Do. 


May 2S.« 

June 3-5 














Weevils marked vellow— 492. 


June 13 


129 

27 

3 














June23-July 5 

July 23-2G 


9 



18 



9 

1 








2 


2 


Weevils marked white— 78. 






Total 


2,318 


159 


9 


IS 


10 


2 


2 


2,518 





a Eighty-seven weevils removed from field May 28 for other experimental work. 

It is ovident from an examination of the number of weevils found 
tliat tlie number in tlie field increased steadily until after Jiuie 5. 
Between June 5 and 13 a large numl^er of previously marked weevils 
a])peared, all of which were undoubtedly hibernated. The very 
small number of first-generation weevils wdiich was found upon the 
examination made between June 23 and July 25 w^as (hie primarily 
to the exceptionally severe hot dry w^eather which had prevailed for 
several weeks. The gradual decrease in the number of living hiber- 
nated weevils was greater than the increase in the number of first- 
generation weevils. During the period between the middle of June 
and the middle of July the plants rapidly increased their fruiting 
activity and there was a decided decrease in weevil injury. It is 
interesting to note that in spite of the large number of hibernated 
weevils occurring in this field, wdiich threatened early in the season 
to jirevent entirely the setting of fruit, the weevil injury and devel- 
opment were so checked by the heat and drought that after the 
middle of July these plants set fniit rapidly and the field produced 
an average yield of cotton. 

The most plausible explanation of the late period of emergence for 
weevils found in this field is the existence in its immediate vicinity 
of a large number of trees wdiich were loaded with long S])anish moss. 
(See PL II, figs. 1, 2.) The explanation of the effect of this moss in 
]>roducing late emergence from hibernation will be considered more 
])ai-ticiilaily in connection with the cage experiments in hibernation 
for 1<)()6 to 1907. 



LARGE-CAGE EXPERIMENTS, l!K¥)-7. 55 

LARGE-CAGE EXPERIMENTS, DALLAS, CALVERT, AND VICTORIA, 

TEX., 1906-7. 

PLAN OF EXPERIMENTS. 

Profiting: by the work done during former seasons, plans were made 
by Mv. W. D. Hunter, in charge of the investigations, for much more 
careful and extensive work diu'ing the winter of 1006-7 than had 
ever been undertaken. Three localities for the experimental work 
were selected representing in a general way the northern, central, and 
southern sections of the State. In these localities, also, much work 
had previously been done and the results for more than one season 
could therefore be used in a comparative way. At Dallas, Calvert, 
and Victoria screen-covered cages were erected, each being 20 feet 
wide, 50 feet long, and about 6^ feet high. (PI. VI, figs. 1, 2, and 3.) 
These cages were divided into ten sections by partitions, each section 
having a ground area of 100 square feet. The three localities selected 
offered a considerable range in geographical and climatic conditions. 
Each section of the cage was provided with a door opening to the 
outside through which access could be had to a section without 
disturbing the conditions in any other section. It was planned to 
provide similar conditions of shelter in corresponding sections and 
to confine weevils in corres]>onding sections at as nearly the same 
date as might be possible in each of the three sections. The weevils 
used were collected in the immediate locality where they were placed 
in hibernation. In this way it was anticipated that data might be 
obtained bearing especially upon the following points: 

(1) The effect of the time of entrance into hibernation upon the 
survival of weevils. In the experiments first started it was necessary 
to force entrance into hibernation, if possible, or starvation by the 
destruction of the food supply. The geographical range was expected 
to increase the interval between the beginning of the experiment in 
each locality and the time when weevils would normally liibernate. 

(2) The effect which the complete destruction of food supply at 
varying dates might have upon the success of hibernation. For these 
experiments the shelter conditions were as uniform and as favorable 
as it was possible to make them in the different localities. It was 
hoped through these tests to determine the minimum interval which 
must elapse between the destruction of stalks and the successful 
hibernation of the weevils. 

(3) To determine the effect of exceptionally favorable and unfavor- 
able conditions of shelter upon the hibernation of weevils placed in 
the cages upon the same date. It was intended that the shelter 
conditions provided should be so exaggerated as to represent the 
extremes of conditions wliich might naturallv occur in the field. 



5G HIBERNATION OF THE COTTON BOLL WEEVIL. 

(4) To determine the effect which diU'erent depths and chisscs of 
shelter might exert upon the success of liibernation and also upon the 
time of emerjjjence and the range of the emergence periotl. 

(5) To test the power of adaptation which the weevils miglit have 
acquired to varying climatic conditions by bringing weevils from 
wi(l(^ly separated localities for comparison with weevils collected at 
Dallas. In each test similar conditions of food and shelter should 
exist in each locality. 

(6) To determine upon a large scale, in very widely separated 
localities, the proportion of weevils entering hibernation which might 
survive. 

(7) To determine the relation between climatic conditions and the 
emergence period in each localit}^. To provide suitable and reliable 
data for this study, standard Weather Bureau instruments were 
secured and temperature, humidity, rainfall, and other records were 
kept in each locality throughout the period covered by the experi- 
ments. 

(8) To determine the longevity of hibernated weevils, especially 
after emergence. Since all weevils used in this work were collected 
promiscuously in the field immediately preceding their confinement 
in the cages, all figures showing their longevity must be based either 
upon the date when they were placed in hibernation or upon the date 
of their emergence. In the latter case it would be distinguished as 
longevity after emergence. 

It was planned to use from 2,500 to 3,000 weevils in each section 
of the cages, although difficulties in the collection of the desired 
number for the particular dates when experiments were to be started 
occasionally caused some variation in this number. Adult weevils 
only were used in sections 1 to 0, inclusive, in each cage, while in sec- 
tion 10 the hibernation of weevils in bolls was tested. One-half of 
the bolls were buried under 2 inches of dirt. The other half were 
exposed upon the surface of the ground. (PI. X, fig. 1.) 

It is generally understood that the principal factor producing a 
hibernation period is the lower temperature occurring during the fall 
and winter months. In its effect upon the survival during this period 
moisture is also an important factor. As a rule, in studies of these 
factors investigators have been obliged to rely upon the climatic 
reports published by the United States Weather Bureau for the par- 
ticular locations desired. It happens frequently, however, that 
there may be no report from the Weather Bureau for the particular 
locality desired. Both temperature and rainfall are liable to con- 
siderable variation within comparatively short distances. In order 
that the data for these studies of the hibernation of the boll weevil 
might bo complete and thoroughly reliable, we have kept full climatic 
records in the immediate vicinit}'' where experiments and cage obser- 



3ul. 77, Bureau of Entonnology, U. S Dept. of Agriculture. 



Plate VI. 






Cages for Hibernation Experiments in Texas, 1906-7. 

Fig. 1.— Dallas, Tox., cage on flat, black-waxy laiiii. Fig. i;.— Calvert, Tex., cage cm slightly 
sloping, .sandy land in post-fiak region. Fig. 3. — Victoria, Te.x.. cage on .sandy-loam slope 
between bottom and npland. (Original.) 



LARGE-CAGE EXPERIMENTS, 1906-7. 



57 



vations have been made. The instruments used are of standard 
Weather Bureau type (PI. I, fig. 1) and, as the records extend over 
several 3'ears, rehable data have been secured upon the following 
climatic factors which may affect hibernation: Maximum and mini- 
mum temperatures supplemented by a continuous temperature 
record made by a recording thermograph; the actual ramfall as meas- 
ured in a standard t^^pe of rain gauge; the atmospheric moisture exist- 
ing at 8 or 9 o'clock a. m. and 5 to 6 o'clock p. m., supplemented by 
a contmuous record of the moisture in the air furnished by a hygro- 
graph. 

Table XXX. — Outline of hibernation experiments in 1906-7. 



No. 
of sec- 


Date of starting experiments 
in 1906. 


Cliaracter of slieltor supplied. 


Food supply. 


tion. 


Dallas. 


Calvert. 


Victoria. 






1 

4 


Oct. 13 
Oct. 16 
Oct. 19 
Oct. 25 

Oct. 31 

Nov. 6 

Nov. 12 

...do 

Nov. 28 
Dec. 6 
and 10. 


Oct. 13 
Oct. 19 
Nov. 26 
Oct. 25 

Oct. 31 

Nov. 5 

Nov. 14 
Nov. 12 
Nov. 25 
Dec. 3 


Oct. 25 
...do.... 


Leaves and grass, 4 to ."> inches . . . 
do 


All food removed uflrr two days. 
Stalks cut down and loft to dry. 


2 


Oct. 28 
Nov. 6 

Nov. 10 

Nov. 14 

Nov. 21 

...do 

Nov. 28 
Nov. 29 


..do 


All food removed after two davs. 


7 

8 
5 


Spanish moss hung on string at 
top of cage; loose bark on 
ground. 

Leaves and grass 4 to 5 inches 
deep, 
do .... 


Stalks cut down and allowed to 
dry. 

All food removed after two d ays 

Cotton cut down and allowed to 


3 
9 
6 


Leaves and grass, 2 inches 

Leaves and grass, 10 inches 

Ground absolutely bare 


drv. 
Do. 
Do. 
No food sujiply. 


10 


(«) 



1 In this section, 3 bushels of probably infested bolls were exposed on the surface of the ground in one half 
of cage, and 3 l^ushels were buried under 2 inches of dirt in the other half. 

The dates given in Table XXX are the actual dates of beginning 
the experiment in each locality. The arrangement of the experiments 
shown in the table is primarily chronological, without regard to the 
sequence in the number of sections. Some knowledge of the plan of 
this work is essential to a clear understanding and a correct interpreta- 
tion of the results obtained from it. 



CLIMATIC CONDITIONS PRODUCING HIBERNATION AND ACTIVITY OF 
WEEVILS DURING NORMAL HIBERNATION PERIOD. 

The climatic records are started with October 1, 1906, in order 
to show a comparison between temperature conditions imder wdiich 
weevils are normally very active with those under which they become 
inactive. The termination of what is considered as being the hiber- 
nation period is rather arbitrarily set at the time when weevils begin 
to emerge in considerable numbers. It should be stated that in each 
locality the climatic records for the winter of 1906 were very unusual. 
The principal points of variation will be noted in subsequent para- 
graphs in their most important connections. In each chart (figs. 3-5) 
showing temperature conditions it has been deemed advisable to 
show only the line rc^presenting the mean average temperature. 



58 HIBERNATION OF THE COTTON BOLL WEEVIL. 

While it is probable that a study of maximum and miniuuim tem- 
peratures is really more aecurate, from a seieiitific point of view, 
the mean average temperature, representing one-half of the sum of 
the maximum and minimum for each day mil be sufficiently exact 
and a more simple manner of expressing the relationship existing 
between temperature and weevil activity. The significance of the 
term "efl'ective temperature" has previously been explained (p. 24). 
Up(Hi the temperature charts the line representing 43 degrees is 
therefore exceptionally emphasized. Wherever the temperature line 
is above this pciint it represents effective temperature. Whenever 
it falls below the 43-degree line it is possible that frosts may occur 
if other atmospheric conditions are coincidently favorable. 

Whenever the minimum is noted to be 32 degrees or below, the 
actual temperature occurring is given in its appropriate place upon 
the record. When the temperature rises above SO degrees, establish- 
ing a new maximum, the occurrence is also shown by the actual 
record given upon the charts. 

vSince it is impossible for weevil emergence to occur at any temper- 
ature below 43 degrees, that point is considered as initial in the fines 
giving the records of the activity of weevils. The actual number of 
weevils found active at various dates is shown at the top of the line 
in each case. 

ENTRANCE INTO HIBERNATION. 

In each locality there occurred a considerable decrease in tempera- 
ture during the month of October, the minimum being reached al)out 
the 31st. This, however, was not sufficiently cold to cause weevils to 
hibernate in considerable numbers. During the following two weeks 
tlie temperature ranged as high as the average for October. After 
November 15, however, there occurred a very marked fall of tem- 
perature, the minimum even as far south as Victoria establishing 
itself at about 25 to 27 degrees. All cotton was killed by this freeze. 
The count of weevils found active early in November indicated 
merely that few weevils had entered hibernation at that time. Fur- 
ther counts, made about November 30, showed that even so severe a 
drop in temperature as had occurred ditl not immediately drive 
weevils into hibernation. During the succeeding two or three weeks 
the tem})eratiire again ranged fully as high as during October, and 
apparently many weevils which had sought shelter after the freeze of 
the night of November 19 again became active. This was indicated 
by the large number of weevils found active at Calvert and Victoria 
about December 10. About the middle of December another period 
of low temperature occurred, which was followed by decreased activity 
among the weevils, many of which did not, even then, seek shelter. 
During the first three weeks of January the exceptionally warm 
weather experienced throughout Texas drew a considerable number 



LARGE-CAGE EXPERIMENTS, 190G-7, 



59 




60 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



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G2 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



of weevils from shelter. During the last week of January and the 
first week of February the lowest temperatures of the winter occurred 
at Dallas and Calvert. The counts made immediately after this 
period showed the smallest number of active weevils recorded at any 
time during the winter for those two localities. At Victoria the tem- 
perature was not sufficiently low to j^roduce any marked decrease in 
weevil activity. During the remainder of February there was a 
rather steady rise in temperature throughout the State and many 
weevils continued active. The figures show that during the last 
week of the month considerable numbers were emerging from their 
winter shelter; and beginning with March 1 the period of general 
emergence is considered to have begun. 

While these three charts show plainly the conditions existing during 
the winter of 1906-7, proving beyond question that during this 
season there was no such thing as complete hibernation of the boll 
weevil in Texas, it must not be understood that this is frequently the 
case. No other such season has occurred since the weevil entered Texas. 
As a rule, hibernation is complete during the period of from four to six 
mcmths. It is certain that weevils may continue their activity 
throughout the season wherever climatic conditions are not sufficiently 
severe to entirely destroy the growth of cotton. 

ACTIVITY DURING NORMAL PERIOD OF HIBERNATION. 



The general impression as to the activity of weevils tluring the 
normal period of liil)ernation has been shown in figures 3 to 5. A 
summary of the records for the three locations, with the temperature, 
conditions prevailing at the time of each examination, is shown in 
Table XXXI. 

T.viiLE XXXI. — Adivity (luring vormul hibernation pcrio'l, 19()(]-7 . 

DALLAS. 



Date. 






Weevils 


counted in section 


- 






Total 
weevils 
count- 
ed. 


Tempera- 
ture. 




1. 


2. 


3. 


4. 


5. 


6. 


7. 


8. 


9. 


10. 


Max. Mean. 


1906. 


230 
02 

4 


290 
96 

12 




102 






315 








937 
1.58 
28 
175 
114 
150 

248 
310 
109 
54 
123 


79 
86 
51 
62 
66 
73 

82 
73 
64 
80 


°F. 
64.0 


Nov. 10 












67.5 


Do 






12 
33 

1.5 
20 

28 
33 
17 
9 
21 






:::::: 


38.0 


Nov 2S 


130 
19 

48 

39 

68 
2.') 

7 


1 

. 2 

5 

7 
in 
3 

3 


""'21' 
4 

7 


4 
9 
8 

13 
15 
4 
4 
14 


7 
11 

7 

11 

15 

...... 

5 






.54. 


Dec. 21 


5 

8 

it 
1.-) 
4 
1 
3 


23 
10 

18 
24. 

5 

4 

4 


12 

19 

43 
.55 
16 
22 
50 


18 
25 

80 
70 
14 
2 
9 


48.0 


Dec. 27 


64.0 


1907. 

Jan. 1 

Jan. 12 

Jan. 24 

Feb. 12 


69.5 
68. 
48.5 
4.5.0 


Feb. 19 


65.0 




341 


486 


341 


140 


188 


32 


386 


57 


217 


218 


2,406 













u This total represents 7.8 per cent of all the weevils put in the cage. 



LARGE-CAGE EXPERIMENTS, 190G-7. 63 

Table XXXI. — A,'tiviti/ t/uring normnl hibernation period, l!)(>6-7 — (Vnitiiiued. 

CALVERT. 



Date. 






Weevils counted in section- 


- 






Total 
weevils 
count- 
ed. 


Tempera- 
ture. 




1. 


2. 


3. 


4. 


5. 


0. 


7. 


8. 


9. 


10. 


Max. 


Mean. 


1906. 
Nov 17 


17 
3 
4 

11 
3 
1 
3 
1 
3 






28 
9 
4 

12 
7 
1 





233 
6 

8 

10 
7 
3 
1 
2 
2 


"217" 

90 
63 
37 
28 
43 
36 


28 
6 


3 
2 
1 
1 
2 

1 


161 
10 
17 

12 
4 

5 
4 
2 
1 






467 
442 
397 

299 
1.59 
86 
75 
91 
69 


°F. 


°F. 


Nov 29 


214 

47 

08 
30 
13 
12 
13 
10 


5.5 
30 

41 
22 

7 
5 
6 
5 


139 
09 

50 
20 
17 
21 
22 
11 


...... 

2 
1 
1 









Dec. 22 


CO 

82 
62 
50 
75 
79 
74 


•is. 6 


1907. 
Jan. 14 


70.0 


Jan. 21 

Jan. 28 


47.0 
39.0 


Feb. 11 


52. 


Feb. 18 


62.0 


Feb. 25 


()5. 


Total 


46 


407 


171 


61 


272 


514 


44 


216 


349 


5 


a 2, 085 


. . ..! .... 

1 



VICTORIA. 



1906. 
Nov ''5 


133 


204 


"34.5" 
163 

lOS 

"i23" 
89 
91 
75 


1.59 












496 

1,7S2 

418 

708 

253 
404 
729 
599 
442 
312 


74 
73 
47 

65 

77 
77 
66 
60 
74 
70 


60. 5 


Dee. 10 


504 




64 


.546 


323 
236 


"'"ill' 


.59. 5 


Dec. 19 






40.0 


Dec 21 


62 

"i47' 

OS 
48 
55 
49 


95 

'"sg" 

50 

55 
40 
28 


06 


186 


81 


18 


200 


51.5 


1907. 
Jan 7 


1.34 


11 


73.0 


Jan 14 


02 
27 
40 
21 
13 


""'69' 
85 
65 
66 


106 
76 
46 
46 
31 






72.0 


Jan. 21 

Feb. 4 


ie 
43 

18 
50 


106 
67 
29 


189 
123 
74 


5 
3 
3 


52.5 
50.0 


Feb. IS . 


02.0 


Feb '^6 


06.5 












562 


561 


994 


388 


975 


386 


209 


948 


1,079 


41 


6 6,143 













n This total represents 10.5 per cent of all the weevils put in the cage. 
Ij This total represents 27.7 per cent of all weevils put in the cage. 

It is hardly proba])le tliat a majority of the weevils may have 
been counted upon two or more dates, but the fact that dead weevils 
were found clinging to the wire (PI. VII, fig. 1) at the time of each 
examination indicates a considerable mortality among the active 
weevils and that the places of the dead ones in successive counts 
were taken by weevils which had become active since the preceding 
examination. The percentages of active weevils for the three local- 
ities show a rather significant difference, and are given for the sake 
of this comparison without presuming to state correctly the actual 
percentage of weevils placed in hibernation which remained active 
during the winter in the respective localities. At Dallas the 2,400 
weevils counted during the winter constitute 7.8 per cent of the total 
num])er placed in hibernation. At Calvert the 2,085 active weevils 
constitute 10.5 per cent of the 19,408 placed in the cage. At Vic- 
toria the 6,143 active weevils constitute 27.7 per cent of the 22,463 
in the experiment. Since approximately the same number of exam- 
inations were made in each locality the differences in percentage 
indicate in a general way the relative activity in these sections of 



64 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



the State. Thus at Dallas 8, at Calvert 1 1 , and at Victoria 2S out 
of every 100 weevils placed in hibernation might have been active 
during the winter. Of course, it is likely that many weevils were 
coimted twice. On the other hand, to counterbalance tliis dupUca- 
tion in the number recorded, it shoukl be statetl that undoubtedly 
many weevils were active at intervals between the counts which 
were either upon the ground or had returned to the ground before 
the examinations were made. Only those weevils which were found 
crawling upon the wire covering of the cage were recorded. The 
temperature conditions as shown for the dates of examination indi- 
cate that there would be no physiological difference in normal weevil 
activity upon those dates. The sectional totals indicate that vari- 
ations in the class of shelter in the different sections exerted little, 
if any, effect upon the activity of weevils during the winter, with 
the exception that Spanish moss seemed to keep more weevils from 
becoming active than did any other shelter. 

WINTER ACTIVITY. 



In most instances when the active living weevils were recorded 
those which were found dead clinging to the wire were collected 
and counted for each section. Undoubtedly a great many weevils 
fell from the screen before or after dying, so that the records are 
very conservative in showing the mortality occurring between exam- 
inations. These records should be considered in connection with 
weevil activity, since the collection of dead stages prevented their 
accumulation upon the wire, and the number found at each exam- 
ination must be considered of those surviving and remaining on the 
wire from a preceding examination and those which emerged subse- 
quently thereto. 

Table XXXII. — Snininury of winter activity as shown by counts of dead weevils. 

DALLAS. 





Date. 


Number of dead weevils found in section— 


Total 
num- 




1. 


2. 


3. 


4. 


5. 


0. 


7. 


8. 


9. 


10. 


ber 

of 
dead 
wee- 
vils. 




1907. 


2 


2 

1 


3 
1 

2 

3 


4 


1 


34 
2 




10 


7 


10 


4 


75 




3 




2 
4 
3 




2 


"672 
7 
1 






2 
6 
3 


5 
7 
1 


aCS7 


February 12 


1 i 5 
1 3 


I 


1 


38 




13 












TotaL. 


5 


9 


13 


3 4() 


(580 


14 


8 


21 


17 


ft 816 











a Of these, 022 were on cloth on ground, having fallen from the wire. 
b This total represents 2.0 per cent of all the weevils put in the cage. 



Bui, 77, Bureau of Entomology, U. S. Dept. of Agriculture. 



Plate VII. 



■7* 







Shelter Conditions, Dallas, Tex., Cage. 

l.-jo. 1.— Active wet'vils trviii.if to escain- thr(iu!,'li wiir on OcIoIht JD. ['M'>. V\ii. 'J.— Section 1, in 
wiiieli weevils were ]ilaiT(i(iiti)ljcr l:;. l'.H)(',, -J.dl j.ri- cent slirvi\in.t;. Fig. Ij.— Sei'tion I, started 
October 16. lyuO, l.UT |kt cmt snrvivin.t;. ( oriuinnl. ) 



LARGE-CAGE EXPERIMENTS^ 1906-7. 



65 



Table XXXII. — Summary of iv inter activity as shown by counls of dead vjeevils — Con. 

CALVERT. 





Date. 




Number 


of dead weevils foiuid in section 


- 




Total 
num- 




1. 


2- 


3. 


4. 


5. 


6. 


7. 


8. 


0. 


10. 


ber 
of 
dead 
wee- 
vils. 




1900. 


121 

14 
1 

5 

1 

1 







3G 

7 
7 

2 

""o 

2 




83 

39 

5 

5 
5 


...... 

10 
12 


6 
2 







1 


47 

20 

4 

3 


3 
2 







293 






2 
3 

4 


101 
1(5 

3 

12 


34 

7 

10 


" "3' 

9 


2 

1 




'0 



220 


December 22 


47 




1907. . 


43 


January 21 


35 




1 


February 11 


5 
4 


5 
3 
1 







12 
4 



30 




23 




2 








Total.. 


143 


18 


141 


54 


137 


41 


9 


79 


09 


3 


1694 







VICTORIA. 



November 25 


loor.. 


8 


13 


""2 
3 



'"u 

. 9 
7 
4 


14 




1 






35 


December 10 


C 




2 


10 


3 

2 


'"'6' 


29 


December 19 




5 


December 24 . 


3 


7 


19 


11 




5 


6 


51 


January 7 . 


1907. 











January 14 


3 

6 
9 
6 
9 


4 

10 
8 
2 
11 


5 
6 
9 

8 
5 


'"i-i" 

10 

4 

11 


2 
4 
1 
1 

5 






14 




2 
9 

i 


12 
14 
12 


5 

11 
11 


2 
1 



71 


February 4 


67 


February 18 


51 


February 26. -- 


45 














Total.. 


44 


55 


37 


59 


54 


13 


11 


60 


32 


3 


''368 







" This total represents 3.6 per cent of all the weevils put in tlie cage. 
*> This total represents 1.7 per cent of all the weevils put in the ca.ae. 

In the section of the table containing the records for Dahas the 
large number of weevils found dead in section 6 on January 24, 1907, 
may be explained by the statement that no previous collection of 
dead weevils had been made in this section. All but 50 of the wee- 
vils found were upon cheesecloth stretched horizontally across the 
section above the ground. The full number is included merely to 
indicate the proportion of weevils wdiich probably fall to the ground 
upon dying. In this section less than 20 per cent remained upon 
the screen, and it is reasonable to suppose that a similar proportion 
may have existed in other sections. The percentage of mortality in 
each place is much smaller than the percentage of living weevils. 
Upon the charts shown in figures 3 to 5 the number of dead collected 
is indicated by a broken line extending beyond the line representing 
the number of living weevils. 
90317— Bull. 77—09 5 



66 HIBERNATION OF THE COTTON BOLL WEEVIL. 

ACTIVITY AS SHOWN BY DEVELOPMENT DURING NORMAL HIBERNATION 

PERIOD. 

Under the lieadiiiji; ''Stages entering hibernation" the ])rincipal 
data bearing upon developmental activity dining the winter have 
been given. (See })p. 13 and 14.) Additional data have also been 
given in connection with ''Shelter dnring hibernation." (See Table 
VII, p. 2G; also Table IX, p. 2S.) To these records for seasons pre- 
ceding 1906-7 may be added the results of an experiment in collec- 
tion of infested squares during this season. On November 23, 1906, 
Mr. J. D. Mitchell collected 100 fallen squares which were supposed 
to be infested. These were placed in the small cage under shelter 
and out of the reach of sunshine. On February 10, 1907, he found 
that 45 squares showed weevil emergence hulls, and the full numl^er 
of adults was found; however, all were dead at that time. An exam- 
ination of the remainder of the squares revealed but one dead larva. 
The others, apparently, had contained no weevil stages. Exception- 
ally warm weather hail prevailed dining December and January, as 
has been shown in figure 5. This had enabled the weevils to com- 
plete their development and emerge, but all had starved to death in 
the absence of any food supply. 

Some very interesting facts are also brought out by a closer study 
of the records in connection with section 10 of each cage. As has 
been shown, the experiment in these sections consisted of the collec- 
tion of large numl)ers of unopened bolls prol)abl3' infested. Several 
of the l)olls were buried under 2 inches of dirt and the remainder 
were exposed upon the surface of the ground (PI. X, fig. 1). No 
partition was inserted to separate the weevils emerging from these 
two lots of bolls, l)ut in the case of section 10 at Dallas the first lot 
of bolls was buried and a considerable period elapsed before the bal- 
ance of the bolls, whicli were left upon the surface, was placed in 
the cage. It was estimated that 3,000 bolls were buried at a uniform 
depth of 2 inches under cover of heavy black soil. An examination 
of 100 bolls showed 8 recentl}^ transformed but unemerged adults in 
the bolls and 8 adults which hatl emerged were hibernating within 
the protection afforded by the bolls. On this basis it appears that 
about 480 weevils were buried in this lot of 3,000 bolls, half of them 
being unemerged adults and half hibernating adults. No other mate- 
rial was placed within this section, so that all weevils which were 
subsequently found uj^on the screen must necessarily have found 
their way through the 2 inches of soil under which the bolls were 
buried. Counts made before the bolls to be placed on the surface 
were put into the cage showed that 65 weevils at least had escaped 
from the bolls to the screen forming the cage. This shows that fully 
13.5 per cent of all the weevils buried, emerged and imemerged, had 



EMERGENCE FROM HIBERNATION, 1907. 



67 



succeeded in escaping. Und()u])tedly part of these had loft their 
cells in the l^olls after they were buried, as it is very likely that the 
burial of the l)olls in moist soil may soften the hulls so as to enable 
the weevils to escape through them as readily as though thvy remained 
dry upon the surface of the ground. 

ACTIVITY IN THE FIELD DURING NORMAL HIBERNATION PERIOD. 

For a number of years it has been known that, in southern Texas 
especially, weevils may frequently be found moving actively in the 
field during the winter, but the observations made during the season 
of 1906-7 extended the range of such occasional activity even in 
northern Texas. 

Table XXXIII. — Outdoor activity of irecvils diiriinj vintrr of i;)06-7. 



Locality. 


Dale. 


^^'^ovils 
found. 


Sprout 
plants 
exam- 
ined. 


Remarks. 


Dallas Tp\' 


1007. 
Jan 1 


1 
1 

1 
2 

9 
10 

9 
20 

1 

4 
1 
1 
3 





Found on awning rope. 

Found on window screen; teniporature 74" F. 
Found on outside of hibernating cage; tempera- 
ture 75° F. 
Do. 
Feeding on sprout cotton. 

When given .sprouts, all were feeding in so min- 
utes; temperature S2° F. 

When given sprouts, all were feeding in 45 min- 
utes; temperature S2° F. 

Mean temperature, Januarv 1-s, =67.76" F. 
On black laml. 

1(1 \^;'i'\'U< ill lw.ll>; nil fhn conn, ulnnt 


Do 

Do 

CoUeue Station, Tex 

Do 


Jan. 11 
Fel). 12 

Feb. 22 
Jan. 17 

1906. 
Deo. 29 

...do 

1907. 
Jan. 8 
Jan. 9 
Jan. 12 
Jan. 16 

.do 


Do 


Do. 


(i 
50 


Do 

Do 

Do. 


Do... . 


30 


Do 

Do. 


Jan. 17 
Jan. 18 
Feb. 14 
Feb. 21 


S 
17 
25 
50 




Do 


Upland sprouts not killed as in l)ottoms. 
Very dry for sprout growth. 


Do. 





« Record not kept, though plants were examined. 
'' Sprout cotton on six farms examined. 

Fi-om the Victoria records it appears that between January 8 and 
February 21, at a time when weevils should normally have been in 
complete hibernation, 48 adults were found feeding on about 200 
sprout plants. This record is unique for the United States, and a 
similar activity in the field may not be duphcated except under very 
rare conditions. 

EMERGENCE FROM HIBERNATION, 1907. 

As is plainly shown by figures 3 to 5, the actual i)erio{l of general 
emergence from hibernation began in each locality about February 20. 
As has been pi-eviously stated, the actual date of the beginning of 
emergence can not be positively given. It can be better expressed 
as a period of ''beginning emergence," and for this reason this period 
seems to lie between February 20 and March 1. Owing to the excep- 



68 HIBERNATION OF THE COTTON BOLL WEEVIL. 

tional earlinoss of the season preparations for the regidar observations 
upon emergence from hibernation were not siifTiciently com|)lete for 
beginning the work until JMarch 1 and in each locahty this date may 
very reasonably be considered as the beginning of the emergence 
period. 

Previous experience having demonstrated the necessity of keeping 
the records upon this work according to a uniform system in each 
locality, the preparations were much more elaboratel}^ made than for 
any previous work. Comprehensive forms upon which the records 
might be entered with a minimum of labor were prepared covering 
five distinct divisions of the work: (1) Meteorological record; this 
record covered maximum and minimum temperatures, atmospheric 
humidity, rainfall, sunshine or cloudiness, and winter conditions. 
(2) Emergence record; this record showed the emergence in each 
section for each date. The records for one week were placed upon a 
card so that the totals for emergence for each day, and also for each 
section for each week, could be very readily ascertained. (3) Section 
record; this covered in more detail the emergence in each section 
and indicated the sex of emerging weevils and what disposition was 
made of them, in such a way that their records could be followed imtil 
the time of death. (4) Longevity records for fed weevils. (5) Lon- 
gevity records for unfed weevils. 

This systematization of the record work has proved an invaluable 
help in compiling the results of this extensive series of observations. 
The general facts regarding the relationshij) existing between climatic 
conditions and weevil emergence are indicated graphically in figures 
6 to 8. The most important conclusions upon special points can only 
be shown by special arrangements of the data in each case. These 
tables have been made as concise as seems possible. Practically each 
line in the tables expresses only the summary of a large number of 
compiled records. The magnitude of the work involved in the com- 
pletion of such tlata can be appreciated onl}" by one who has under- 
taken a similar task." 

RELATIONSHIP OF EMERGENCE FROM HIBERNATION TO CLIMATIC CON- 
DITIONS. 

Figures G to 8 have been prepared in the same form as figures 3 to 
5, since they express a continuation of similar facts. 

In former reports/' dealing especially witli the life history of the 
boll weevil, it was stated that emergence began about the time 
when the mean temperature rose above 60° F. The more complete 

o The senior author desires to ex|)ress particular appreciation of the great amount of 
detail work which has been done by the junior author (Mr. W. W. Yothers) in the prep- 
aration of the summaries covering this work. 

bJJ. S. Dept. Agr., Bur. Ent., Buls. 45 and 51. 



EMERGENCE FROM HIBERNATION, 1!)07. 



69 



records now at hand indicato that, emergence may take place when- 
ever the mean average temperature exceeds 55° F. It is certain 
that weevils may be active at a temperature considerably lower 
than this, but the records do not indicate that there is a general 



RAINFALL /N INCHES 
o 7- — ro fo 

o « § S g ^ 


■*H 












«i 
















































*^ 


•^ 










N 
















































==^ 


-i 










S 


■S 




















^ 


^ 


































.._ 














— 




H 






N 
























a— . 


— 


— t 




















t 
























^ i> ~ i~ f^ ^ 

/^/NFALL 7n /NC»SS 







emergence from hibernation at a lower temperature. After having 
left their winter quarters, weevils may continue active at consideral)ly 
lower temperatures than are required to draw them out from their 
shelter. This statement may, in i)art at least, explain the continued 



70 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



activity of weevils during the winter of 1906-7 and the early beginning 
for the period of emergence for that season. 




S 8 S § S 

<vj pj _ _: O 


































•^^ 


■ 
























K^ 
















































'^ 








s 


























- 




















' 


"^ 










l». 


N 












^ 








N 


-^ 


-■lii^ 










ta 


-i 




















































































^ 












1 














K i s § s ° 

ry C\J — • — o 
S3HOM N/ -nbaNltT'id 



A com]3arison of figures 6, 7, and S indicates that the period of great- 
est emergence in each locality occurred during March, 1907. The 
abnormal nature of temperature conditions is shown by the fact that 



EMERGENCE FROM HIBEENATION, 1901. 



71 



at Dallas the mean average temperature for the month was over 11 
degrees above the normal. At Calvert the departure was about the 



.^1 8 g 










































1 






























^1 


■S 








1 














x^ 


■i 






--i 






















N 








==4=»* 


N 




























•^ 
























^ s i § 

RAINFALL /N /NCHSS 




same, and at Victoria it was but slightly less than 10 degrees above 
normal. Such high temperatures do not often occur before the latter 
part of April and the 1st of May. The temperature for April was 



72 



HTBP^-RNATION OF THE COTTON BOLL WEEVIL. 



unusually unfavorable, but in all sections it ranged from 3 to 5 
degrees below the normal. This decrease was not, however, sufficient 
to check the emergence of weevils, although undoubtedly it served to 
extend the period of emergence in an unusual degree. The abnormal 
nature of the temperature conditions for the spring of 1907 may be 
understood from a comparison of the mean monthly temperatures for 
these four months in each case. The normal is determined by the 
Weather Bureau records from an average of the mean monthly tem- 
peratures for the entire period during which records are available. 
The departure of each season, therefore, affects the normal for the 
following season. 

The general impression in regard to the exceptionally high tem- 
perature experienced during the winter of 1906-7 is confirmed by a 
comparison with the average records for a number of seasons. Tem- 
perature alone need be considered in making this comparison, although 
rainfall has an important direct effect upon temperature conditions. 
For the following comparison the records given by the United States 
Weather Bureau are used. As there is no report for Calvert the 
average of two points about equally distant on opposite sides of that 
place is used. 

Table XXXIV. — Mean monthly temperatures and departures from normal at Dallas, 
Calvert, and Victoria, Tex., November, 1906, to February, 1907. 





November. 


December. 


January. 


February. 


Locality. 


Monthly 
mean. 


Depar- 
ture. 


Monthly 
mean. 


Depar- 
ture. 


Monthly 
mean. 


Depar- 
ture. 


Monthly 
mean. 


Depar- 
ture. 


Dallas 


°F. 
54.3 
59.1 
62.9 


°F. 
-0.6 
+ .1 
-1.8 


°F. 
51.6 
56. S 
59.2 


"F. 

+ 3.8 
+ 4.1 
+ 1.4 


°F. 
53.4 
59.8 
63.4 


"F. 

+ 8.5 
+ 9.0 
+ 9.8 


"F. 
51.2 
54.8 
60.2 


°F. 
+6.6 


Calvert 


+ 2.8 


Victoria 


+ 6.2 



It will be noted that the departure from normal during November 
was very slight. The temperature conditions, therefore, during the 
usual period of entrance into hibernation were practically normal, the 
rise occurring during December and January, especially when weevils 
should normally have been in complete hibernation. Table XXXV 
continues the same study throughout the period of emergence from 
hibernation. 

Table XXXV. — Mean average temperatures and departjires from normal at Dallas, 
Calvert, ayid Victoria, Tex., March to June, 1907. 





March. 


April. 


May. 


June. 


Locality. 


Monthly 
mean. 


Depar- 
ture. 


Monthly 
mean. 


Depar- 
ture. 


Monthly 
mean. 


Depai- 
ture. 


Monthly 
mean. 


Depar- 
ture. 


Dallas 


°F. 
66.7 
70.0 
72.4 


°F. 
+ 11.1 
+ 9.2 
+ 9.7 


"F. 
61.4 
62.2 
69.4 


°F. 
-4.2 
-5.9 
-3.3 


'F. 

65.8 
60.6 
73.0 


"F. 

-7.7 
-7.3 
-5.0 


°F. 

78.8 
70.6 
81.6 


°F. 
-1.9 


Calvert 


-4.4 


Victoria 


- .6 



EMERGENCE FROM HIBERNATION, 1901. 



73 



The unprecedented emergence during March is very easily exphiined 
by the remarkable temperature conditions during that month. In 
spite of the fact that emergence began earlier than had ever been 
known previously, it continued later also because of the exceptionally 
low temperatures prevailing during April, May, and June. A com- 
parison of figures 1 and 2 with figures 6 to 8 is interesting and shows 
how strikingly the nature of the emergence movement may vary in 
respect to diflerence in climatic conditions. The careful examina- 
tions made to discover the termination of the emergence period were 
continued for fully two weeks after the last weevil was found. It 
seems impossible to explain the long-delayed emergence of some 
individuals. The lack of an explanation, however, does not alter the 
fact that emergence is probably not generally complete until after the 
middle of June. 



Table XXXVI. 



-Geiural summarij of experiments of 190G- 
hibernation. 



on emergence from 





Number of 

weevils- 


Number 
of wee- 
vils 
emer- 
ging 




Locality. 


Put in 
cages. 


Used as 
basis for 
percent- 
age of 
emer- 
gence, a 


Percent- 
age 
emer- 
ging. 


Dallas, Tex 


.32, 439 
20, 430 
23, 045 


30, 804 
19,408 
22, 403 


3,404 

1,842 

b 3. 020 


11 22 


Calvert, Tex 


9 49 


Victoria, Tex 


13 47 






Total and average 


70, 514 


72,735 


8,332 


11 45 







aBasis for computing the percentage of emergence is 5 per cent less than tlie number of weevils put in 
cages owing to the escape of some weevils through the meshes of the wire. 
b Two weevils not in summary. 

A deduction of .5 per cent from the number of weevils placed in the 
hibernation experiments is made to furnish a more correct basis for 
determining percentages, on account of the fact that experiments 
have shown that about 5 per cent of a miscellaneous collection of 
weevils may be able to escape through 14-mesh wire (PI. VII, fig. 1), 
such as was used in the construction of these cages. The percentage 
of survival is strikingly similar in each locality. The average sur- 
viving hibernation — approximately 11 per cent — is probably the 
highest that has ever occurred since the weevil entered Texas. 
Although observations have indicated that occasionally the per- 
centage of survival may be as high as this in the field, it is fortunate 
for the cotton planter that such is very rarel}^ the case. 



74 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



EFFECT OF TIME OF ENTERING HIBERNATION AND NATURE OF SHELTER 
UPON THE PERCENTAGE OF SURVIVAL. 

One of the most important points upon which information was 
sought tliroiiglioiit these experiments was the effect of time of enter- 
ing hibernaticni anil nature of slieh.er upon the percentage of survivaL 
The first confinement of weevils in the fall occurred fuWy a month 
earlier than the beginning of similar experiments the previous year, 
and it was expected that the intervals between their confinement in 
the cage and the time for successful hibernation might be sufficient to 
plainly reduce the proportion of weevils surviving. 

Table XXXVII. — Chronological arrangement of sectional records shoicing relative 
survival at Dallas, Calvert, and Victoria, Tex., 1906-7. 







Sec- 


When 


tion 


started. 


num- 






ber. 


1906. 




Oct. 


13 


1 


Oct. 


16 


4 


Oct. 


20 


2 


Oct. 


24 


7 


Oct. 


30 


8 


Nov 


5 


5 


Nov. 


12 


3 


Nov. 


13 


9 


Nov. 


15 


11 


Nov. 


21 


12 


Nov. 


28 


6 


Dec. 


6 


10 



Cliamcter of slielter and food. 



Date of 
last 
emer- 
gence. 



Basis 
number 

of 
weevils. 



Total 
weevils 
emerged. 



Percent- 
age of 
survival. 



Rank of 
section in 
survival. 



Leaves and hay, 4 inches deep, cot- 
ton stalks lefto 

Leaves and hay; stalks cut and left 
four days *> 

Leaves and grass 4-5 inches deep; 
no food 

Spanish moss and chips; c cut food.. 

Leaves and grass 2-3 inches deep; 
no food d 

Leaves and grass 9-10 inches deep; 
stalks cut and left « 

Leaves and grass: no food / 

Leaves 8-10 inches deep; green cot- 
ton cut and left g 

Leaves 3-4 inches deep: stalks left 
standing 

do 

Bare ground; no food 

(Bolls ( on surface J 

\Bolls i buried ; 



Total and average. 



1907. 
May 21 

May C, 

May 19 
June 17 

June 15 

May 15 
May 21 

June 19 

June 4 
June 8 
Apr. 29 

[■May 2 



3,800 

2,090 

3,610 
3,325 

2,850 

3,135 
3,040 

3,040 

2,565 

1,.570 

975 

8(54 



226 
231 



250 
383 



30,8l>4 



3,464 



2.61 
4.07 



6. 26 
6.95 



8.85 



12.22 
14.74 



31. .34 

A 4. 14 
4.72 



CALVERT. 



Oct. 

Oct. 
Oct. 
Oct. 

Nov. 

Nov. 

Nov. 

Nov. 
Nov. 
Dec. 



13 


1 


19 


4 


25 


7 


31 


8 


5 


5 


12 


9 


14 


3 


25 


6 


26 


2 


3 


10 



Food, two days; grass and leaves 

4-5 inches deep 

Grass and leaves 4-5 inches deep 

Spanish moss; chips 

Food two days; grass and leaves 4-5 

inches deep 

Food dry; grass and leaves 4-5 

inches deep 

Food cut down, left dry; 10 inches 

grass and leaves ". 

Stalks cut down, left dry; 2 inches 

grass and leaves ". 

Field protection or bare; some grass. 

No food; leaves and hay 

Bolls 



Total and average. 



June 
May 
July 


12 

30 

1 


May 


30 


Apr. 


26 


June 


12 


May 
]\Iay 
June 
Mar. 


31 
Ki 
12 

24 1 









2,375 
2,;J75 
2,375 

2,375 

2,:375 

2,375 

2,375 
1,425 
1,358 
(*) 



19,408 



116 
105 

63 

45 

438 

253 

359 
380 



1,842 



3.15 

4.88 
4.42 

2. 65 

1.89 

18.44 

10. 65 
25. 19 
27.98 



9.49 



aSeePl. VII, fig. 2. 
bSeePl. VII. fig. 3. 
oSeePl. Vni, figs. 1,2. 
d See PI. IX, fig. 1. 
fSeePl. IX,flg. 2. 
/See PI. IX, fig. 3. 
ffSeePl. X,fig. 2. 

A The weevils put in on November 21 were brought from Brownsville, Te.x. The low percentage of 
survival doulitless resulted from their weakened condition, owing to insufficient food during transportation. 
i Bolls presumably infested. 
;See PI. X, fig. 1. 
* No estimate made. 



Bui. 77, Bureau of Entomology, U, S. Dept. of Agriculture. 



Plate VIII. 




Hanging Moss as Affecting Hibernation and Emergence. 

Fig. 1. — Section 7, with hanging moss in top of Ciige. Fig. 2.— Same section, ground conditions, 
started October 24, 1906; (3.95 per cent surviving; emergence ceased June 17, 1907. (Original.) 



Jul, 77, Bureau of Entomology, U S, Dept, of Agiicultu 



Plate IX. 




v^/'-d^ >!' 



Shelter Conditions Producing Average Survival at Dallas, Tex. 

Fig- 1.— Scctiun s. startnl ( Jctdlirr :'.(i, r.ioc,: fiiuTKciice ciusril .liiiii> Ifi, I',HI7; survival, f^.-s," 
cunt. V\%. 'J. — yec-tiiiii .">, ^laitrd Nnvfiiilicr ."i. l',iiii.: (■inrrLrciicu cca'-tMi May T'). 1'.)|I7: sui\ 
\l:rl per ci'iit. V\)i. :;,— Scriicin :;. started Xci\ fiiihi-r ]_', I'.ior,; euRTgeiKX' ('■oa-eil Mav 'Jl, 
survival. 11.71 iier crnl. 1 1 iriyiiial. ) 



ival. 
1'.IU7: 



Bui. 77, Bureau of Entomology, U. S. Dept. of Agriculture. 



Plate X. 




^^^'.^K* ^Jsi> M-^' 4.* ; ^- ' • ~ -.' 'tSjJ^j^^i^'' 



Jm^i.m. 




Exceptionally Favorable Conditions and Boll Experiment. 

Fit,'. 1.— Seetiun lu, a, bolls expo.sed on surface: b, corner wiiere bolLs were buried 2 inches 
deep, started l)ecember 6, 1906: emergence ceased May 2, 1907; survival. 4.51 per cent. Fig. i'.— 
Section 9, stalks left, started November 13, 190t5; emergence ceased June 19, 1907; survival^ 2ri.92 
percent. (Original.) 



EMERGENCE FROM HIBERNATION, 1907. 



75 



Table XXXVII. — Chronological armngemenl oj sectional records showing rehifin 
vival at Dallas, Calvert, and Victoria, Tex., 1906-7 — Continued. 

VICTORIA. 





Sec- 


When 


tion 


started. 


num- 




ber. 


1900. 




()pt. 25 


1 


Do.... 


4 


Oct. 28 


2 


Nov. (') 


7 


Nov. 10 


8 


Nov. 11 


5 


Nov. 21 


9 


Do.... 


■.i 


Nov. 2S 


fi 


Nov. 29 


10 



Chanicfcr of sIieKer ami food. 



Date of 

last 
emer- 
gence. 



1907. 



May 15 

May 11 
June 15 



Weeds and grass 5 inches; stallts left.! May 1 1 
Weeds and grass 5 inches; stallis 

removed 

Weeds and grass 4-5 inclies; stalks 

cut, left 

Moss, l)ark, chips, etc.; no food 

Grass and weeds 5 inches; stalks 

removed 

Stalks pulled, left; grass and weeds 

5 inches 

Grass and weeds 10 iuclies; stalks 

pulled and left 

Weeds and grass 2 inches; stalks 

pulled and left 

Ground hare; no food 

Bollsa 



Total and average . 



May 
Apr. 

May 



23 



...do 

May 
Mai-. 



Basis 
runnlier 

of 
weevils. 



Total 
Vv'eevils 
emerged. 



2,:i75 

2,375 

2,375 
2,850 

2,850 

2,850 

2,850 

2,850 
1,088 
(«) 



22,463 



201 

105 

134 
ti74 

3(>2 

449 

374 

5SS 
l:i9 



3,028 



Percent- 
age of 
survival. 



8. 4() 

4. 42 

5.(il 
23. 05 

12. 70 

1.5.80 

1.3. 19 

20. 03 

12. 78 



Rank of 
seclion in 
survival. 



a Three Inishels of bolls on llie surface, and 3 bushels covered with 2 inches of earth. 

The results of this work are exceptionally striking in the case of the 
Dallas record. The Calvert record ranges between that of Dallas and 
Victoria in regard to the clearness wdth which comparative effects are 
shoW'n. In each case there is, how^ever, a general tendency tow^ard 
more successful hibernation as the season advances after the middle of 
October until the time when frosts occur. In the case of the Dallas 
records there occurred an almost uninterrupted increase in percentage 
of survival with each date upon which experiments were started. 
The apparent exceptions are readily explainable by other facts than 
the time of starting the experiment. Section 12, which ranged sixth, 
received weevils collected at Brownsville, Tex., which made it neces- 
sary to ship for a long distance. During this shipment their food 
supply became ]:)Oor, and the weevils were undoubtedly much w^eaker 
upon being placed in the cage than were those which had been col- 
lected in the immediate vicinity of Dallas. Section 6 was not provided 
with any shelter for the w^eevils, and the percentage of survival was 
smaller on that account than in other sections started at about the 
same date. Section 10, which ranged ninth, received only infested 
bolls, upon and within which weevils were hibernating. From 
October 13 to November 15, under approximately similar conditions, 
the percentage of survival increased from 2.61 to 31.34. (See PI. 
VII, figs. 2, 3.) A more forceful argument than this for the destruc- 
tion of the food supply as early in the fall as is ]:>ossible could hardly 
be given. 

A combination of the records for those localities at which experi- 
ments were started upon the same or approximate dates, grouping 
them so that the chronological sequence is most clearly shown, adds 
additional emphasis to the statements which have just been made. 



76 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



Table XXXVIII. — Comparison of sectional records grouped by approximate initial 

dates. 



Diito. 


Locality. 


S(>ction 
ninnlier. 


Basis 
number 

of 
weevils. 


Total 
number 
emerged. 


Percent- 
age of 
survival. 


Rank in 
percent- 
age of 
survival. 


li)O('). 
Oct. 13 


Dallas 


1 
1 
4 


3,800 
2,375 
2,090 


99 
75 

85 


2.61 
3.15 
4.07 




])() 


Calvert 


\ » 


Oct ICi 


Dallas 




'I'olal and a\'rrai,'e 


) 






8, 2(i5 


259 


3.U 






Calvert 






Oct. 19 


4 
2 


2,375 
3, 010 


116 
22ti 


4.88 
6.26 


) ' 


Oct "0 


Dallas 




Total and average 






5, 985 


342 


5.71 






Dallas... 






Oct. 24 


7 
7 
1 
4 


3,325 
2,375 
2,375 
2,375 


231 
105 
201 
105 


6.95 
4.42 

8. 4ti 
4.42 


1 


Oct. 25 


Calvert 




Do . 




^ 


Do.... 


do 






Total and average 








10, 450 


642 


6.15 






Victoria 






Oct. 2.H 


2 
8 
8 


2,389 
2,850 
2,375 


134 

250 

63 


5.61 
8.85 
2.65 


1 


Oct. 30 


Dallas 


i c 


Oct. 31 




1 




Total and average 








7,614 


447 


5.87 






Dallas. . . . . 






Nov. 5 


5 
5 

7 


3,135 
2,375 

2,850 


383 
45 

674 


12.22 

1.89 

23.65 


1 


Do. 


Calvert 


4 






1 




Total and average 








8, 360 


1,102 


13.18 






Victoria 

Dallas .. 






Nov. 10 

Nov 12 


8 
3 
9 
9 
5 
11 


2,850 
3,040 
2,375 
3,040 
2,850 
2,565 


362 

448 
438 
788 
449 
804 


12.70 
14.74 
18.44 
25.92 
15. 86 
31.34 




Nov. 14 


Calvert . . .. 




Nov. 13 




1 ^ 


Nov. 14 


Victoria 






Total and average 








16, 720 


3,289 


19.67 






Dallas. . . 






Nov. 21 


12 
9 
3 


1,570 
2,836 
2,850 


65 
374 

588 


a 4. 14 
13.19 
20.63 


1 


Do... 
Do... 


Victoria 

.do 


1 ' 












7,251.) 


1,027 


b 14. 15 












Nov. 25 


6 
(i 


1,425 

1,358 

975 

1,088 


3.59 

380 

46 

139 


25.19 
27.98 
f 4.72 

c 12. 78 


1 


Nov. 26 

Nov. 2S 

Do.... 


do 

Dallas 

Victoria 


1 - 






4, 846 


924 


d 19.07 













"Brownsville, Tex., weevils. 

b Average omitting Brownsville weevils, 16.91 per cent. 

c . Absolutely liare ground. 

d Average witliout "Dallas cage, 22.7 per cent. 

In this tal)lo it may be seen that, taking all localities together, 
whenever experiments were started upon approximately the same 
date there is a most striking increase in successful survival at inter- 
vals between the middle of October and the middle of November. 
This table may be safely considered as representing in the most 
general way possible the facts in regard to this point. An interval of 
about eleven days between October 14 and 25 practicall}^ doubled the 
percentage of weevils surviving. Again, in an interval of about ten 
days between October 25 and November 5 the percentage was again 



EMERGENCE FROM HIBERNATION, 1907, 



77 



doubled, and an increase of 50 per cent was observable between 
November 5 and 14. After November 14 hibernation might have 
been successful for practically the maximum possible proportion of 
weevils. The relation of these figures may l^e most sim]:)ly expressed 
in the following manner: Under similar conditions of shelter, but 
without a food supply, if the survival of weevils in Texas for October 
15 is one, for October 25 it will be two; for November 5, four; and for 
November 15, six. These figures make it evident that from October 
15 to November 15 constitutes the strategic ]:)eriod for attack upon the 
boll weevil. The attack can be made in two ways : (1 ) By the tlestruc- 
tion or removal of the con(htions favorable for the shelter of the 
weevil through the winter; (2) by the destruction of the food supply. 
These conclusions have fre([uently been stated and are here repeated 
because the facts here presented prove more conclusively than have 
any other data heretofore obtained the unquestionable importance 
of fall work in combating the boll weevil. The benefit, obviously, 
will always be realized during the following season by a much smaller 
injury to the crop. Considerations, both of minimum expense and 
of maximum efl'ectiveness, emphasize this conclusion. 

SURVIVAL OF WEEVILS BY LOCALITIES AND CAGE SECTIONS. 

In practically all of the sections it may be considered that the 
emergence period began during the last few days of February and 
the first few days of March, March 1 being, approximately, the 
average date in each case. In the following table the summaries of 
the sectional records in each locality are given, together with the data 
necessary to show the maximum length of the hibernation period and 
the percentage of survival in each section: 

Table XXXIX. — Maxitii.uiii. hihcrnatioii period and pirrcntwjc of survival hy sections, 

I'JOG. 

DALLAS. 



Section numlicr. 


When 
installed. 


Weevils 
started. 


Numtjcr 
used as 
basis of 
percent- 
age. 


Date of 
last 
emer- 
gence. 


Total 
weevils 
emerged. 


Percent- 
age of 
survival. 


1 


190(i. 
Oct. 13 
Oct. 20 
Nov. 12 
Oct. 16 
Nov. 5 
Nov. 28 
Oct. 24 
Oct. 30 
Nov. 13 
Dee. 
Nov. 15 
Nov. 21 


4,000 
3,S00 
3,200 
2,200 
3,300 
1,025 
3,500 
3,000 
3,200 
864 
2,700 
1.650 


3, SOO 
3,610 
3,040 
2,090 
3, 135 

975 
3,325 
2, 850 
3,040 

864 
2,565 
1,570 


1907. 
May 21 
May 19 
May 21 
May 6 
May 15 
Apr. 29 
June 17 
June 15 
June 19 
May 2 
June 4 
June 8 


99 
226 
448 

85 
383 

46 
231 
250 
788 

39 
804 

65 


2.61 


2 


6. 26 


3 


14 74 


4 


4.07 


5 


12 22 


6 


4.72 


7 


6 95 


8 


8 85 


9 


25. 92 


10 


4 51 


11 


31.34 


12 


4.14 






Total and average 


32,439 


30, 864 




3, 464 1 1 - 22 













78 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



Table XXXIX. — Maximum liihenuilioa period and percentage of sarvival by sections, 

i.VWfi— Continued. 



CALVERT. 



Softion iiiunlicr. 


When 
installed. 


Weevils 
started. 


Niimljer 
vised as 
basis of 
pereent- 
ago. 


Date of 
last 
emer- 
gence. 


Total 

weevils 
emerged. 


Percent- 
age of 
survival. 


1 


190(3. 
Oft. 13 
Nov. 20 
Nov. 14 
Oft. 19 
Nov. 5 
Nov. 25 
Oft. 25 
Oft. 31 
Nov. 12 
Dec. 3 


2, 500 
1, 430 
2, .500 
2, 500 
2, 500 
1,500 
2, 500 
2, .500 
2, 500 
Bolls. 


2, .375 
1,358 
2, 375 
• 2, 375 
2, 375 
1,425 
2,375 
2, 375 
2, 375 
(") 


1907. 
June 12 
....do.... 

May 31 
May 30 
Apr. 2(3 
May It) 
July 1 
May 30 
June 12 
Mar. 24 


75 
380 
2.53 
116 

45 
359 
105 

03 

438 

8 


3 15 




27 98 


3 


10 05 


4 


4 88 




1 89 


a 


25 19 


7 


4 42 


8 


2.65 
18 44 


9 . ... 


10 








Total ancl avcraijc 


20, 4.30 


19,408 




1,842 


9.49 











VICTORIA. 



1 


Oct 25 
Oct. 28 
Nov. 21 
Oct. 25 
Nov. 14 
Nov. 28 
Nov. 6 
Nov. 10 
Nov. 21 
Nov. 29 


2, .500 
2,515 
3,000 
2, ,500 
3,000 
1,145 
3,000 
3, 000 
2, 985 


2, 375 

2,389 
2, 8.50 
2,375 
2,850 
1,088 
2, 850 
2,850 
2, 836 
C) 


May 11 
....do.... 
May 23 
May 15 
Apr. 28 
May 11 
June 15 
May 6 
Mav 23 
Mar. 4 


201 
134 
588 
105 
449 
139 
674 
362 
374 
2 


8.46 


2 


.5.61 


3 


20 63 


4 


4.42 




15. 86 


6 


1'^ 78 




23.05 


8 


12 70 


9 


13 19 


10 ... 










23, ()45 


22, 463 




3,028 


13.47 











" No estimate made. 



f' Three bushels of liolls on surface and 3 Ijnshels covered with earth. 



The longest period of liibeinatiou occurred at Calvert among the 
weevils placed in section 7 on October 25, the last weevil emerging 
from this section being taken on Jidy 1, 1907. During this period 
of over eight months this weevil survived without a particle of food. 
This may be considered as representing the maximum hibernation 
period, and in the case of an insect producing mimerous generations 
during each season it is surprising that the hibernation period can 
be so greatly prolonged. 

The largest average percentage of survival occurred at Victoria, 
although the variation between the three localities was not unex- 
pectedly great. The natiu'e of the shelter })rovided in each section 
has been indicated upon l^age 57. A com])arison of the records for 
section 7 for Calvert and Dallas with those for the same section at 
Victoria shows that at the last-named ])lace the survival was four 
times as great as in tlie average of Dallas and C ill vert. The shelter 
provided was as closely similar in the case of this section as in any 
of the series, and the significant ])oint of difference appears, there- 
fore, to be the time when weevils were inclosed. At Dallas and Cal- 
vert this occurred on October 24 and 25, respectively, while at 
Victoria weevils were not placed in the cage until November 6. 
Apparently, therefore, the much larger survival at Victoria was due 



EMERGENCE FROM HIBERNATION, 1U07. 



79 



primarily to the starting of the ex|)eriment about twelve days later 
than in the other two localities. 

The significance of the time of beginning the experiments is well 
emphasized by the records for sections 2 and 6 at Calvert. These 
two sections furnished by far the highest percentages of survival at 
that ])lace, aiul apparently the only f;ict explaining this is that the 
experiment was started in each case at the time whicli was most 
favorable for successful hibernation, i. e., about November '2o. This 
date was ten or twelve days later than those for sections 3 and 9, 
which present the next higher percentages of survival. An av(>rage 
of these two sections shows that among the weevils starting hiber- 
nation about Novem})er 12, 14.5 per cent survived, while among 
those starting hibernation about Xovend)er 25, about 20.5 jxn- cent 
survived. 

The records for Dallas show that the three highest percentage's of 
survival occurred in sections 11,9, and o, which were started l)etween 
November 12 and 15. 

In eacli locality the average date for tlie termination of emerg(>nce 
occurred between May 22 and 29. It is evident, therefore, that 
during 1906 the period of emergence from hibernation covered 
practically three months for an average of all of the sections and 
slishtlv more than four months for the last emerged weevils. 



MONTHLY SUMMARY OF EMERGENCE RECORDS. 

Wliile it is important to know, approximately at least, the maxi- 
mum limit of the emergence period, it may seem more desirable to 
determine the time at which a majority of weevils surviving had 
emerged. It is more convenient in using the records to compare 
them in four-week periods rather than according to calendar months. 

Table XL. — Entnyoice in l!)t)7, hy four-irrrk periods. 





Mar. 1-28, wee- 
vils emerged. 


1 
Mar. 29-Apr. 25, Apr. 26-May 23, 
weevilsemerged. weevils emerged. 


May 24-July 1, 
weevilsemerged. 


Total 


T.ocality. 


Num- 
ber. 


Per 

cent of 
total. 


Num- 
ber. 


Per 
cent of 
total. 


Num- 
ber. 


Per 
cent of 
total. 


Num- 
ber. 


Per 
cent of 
total. 


emer- 
gence. 


Dallas 


2,486 
1,053 
2,399 


71.8 
57.1 
79.3 


484 
410 
476 


14.0 
22.3 

15.7 


452 

284 
119 


13.0 
15.4 
3.9 


42 
95 
32 


1.2 
5.2 
1.1 


3,464 




1,842 


Victoria 


3,020 






Total and average 


5,938 1 71.3 


1,370 


16. 4 ! 855 


10.3 


169 


2.0 


8,332 



WEEKLY EMERGENCE RECORDS. 



The following table ])resents a summary of the daily emergence 
records for each section during seven-day periods from March 1 to the 
end of the hibernation period. These records are particularly inter- 



80 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



esting in showint:; tho variation occurring in emergence in the same 
section and locality during the different periods. 

Table XLI. — Suinniarij of emergence of iveevlls in cage sections by ireeklg periods, 

March 1 to June 20, 1907. 

DALLAS. 



Weekly period. 


Number of weevils emerged in section number— 


1. 


2. 


3. 


4. 


5. 


6. 


7. 


8. 


9. 


10. 


11. 


12. 


Mar. 1-7 


40 
8 
17 
10 
4 
7 
1 
1 
5 
2 

2 
2 






69 

36 

39 

21 

20 

13 

6 

5 

10 

3 

2 

2 






155 

51 

85 

38 

19 

30 

12 

8 

16 

21 

10 

3 








30 
10 
11 
8 
3 
7 
. 1 

3 
3 



I 



151 

4(1 

89 

51 

8 

10 

7 

1 

5 

7 

8 










21 

11 

2 

1 
3 


1 








73 

25 
64 
25 
4 
7 
8 
2 
2 
7 
2 
8 

1 
1 
2 


79 

31 

35 

22 

15 

10 

5 

3 

20 

14 

7 

3 

3 

2 



1 


212 

120 

202 

123 

7 

17 

10 

6 

8 

26 

29 

16 

4 

4 

3 

1 


12 
7 

13 
4 
1 
1 


1 












Mar. S-14 


65 

145 

189 

49 

78 

55 

15 

27 

40 

58 

67 

12 

4 




7 


Mar. 15-21 


10 


Mar. 22-28 

Mar. 29- Apr. 4... . 


11 
4 


Apr. 5-11 


11 


Apr. 12-18 


6 


Apr. 19-25 





Apr. 26-Mav2 

May 3-9 


1 
6 


May 10-16 


3 


May 17-23 


2 


May 24-30. . 


1 


May 31-June 6 


2 


June 7-13 


1 


June 14-20 
























Total 


99 


226 


448 


82 


383 


4(i 


231 


250 


788 


39 


804 


65 







CALVERT. 



Mar. 4-7 

Mar. 8-14 

Mar. 15-21 

Mar. 22-28 

Mar. 29- Apr. 4. 

Apr. 5-11 

Apr. 12-18 

Apr. 19-25 

Apr. 26-Mav2. 

May 3-9 

May 10-16 

May 17-23 

May 24-30 

May 31-June 6. 

June 7-13 

June 14-20 

June 21-27 

June 28-July 4 . 



Total . 



380 



136 

47 

45 

57 

22 

21 

16 

6 

3 

3 

3 













359 



105 



VICTORLV. 



Feb. 28 

Mar. 1-7 

Mar. 8-14 

Mar. 15-21 

Mar. 22-28 

Mar. 29- Apr. 4. 

Apr. 5-11 

Apr. 12-18 

Apr. 19-25 

Apr. 26-May 2 . 
May 3-9....".... 

May 10-16 

May 17-23 

Mav24-.30 , 

May 31-June 6. 

June 7-13 

June 14-20 

Total 



39 


24 


69 


13 


60 


35 


29 


32 


23 


95 


20 


80 


29 


36 


54 


30 


130 


22 


103 


24 


63 


36 


18 


94 


19 


88 


25 


124 


18 


10 


54 


13 


58 


18 


170 


9 


6 


51 


9 


17 


5 


19 


3 


8 


44 





26 





04 


5 


5 


28 


5 


7 





47 


1 


1 


9 


1 


6 





11 


1 





4 


1 


4 





14 


o 


2 


8 











31 


1 


i 


1 


2 





1 


20 








1 











. 14 




















8 




















21 




















2 
1 














201 


134 


588 


105 


449 


137 


674 



31 
92 

107 
72 
2() 

15 

8 



EMERGENCE FROM HIBERNATION, 1907. 



81 



There is no indication that the time at which an experiment was 
begun affected essentially the nature of the emergence movement. 
The nature of the shelter, however, does seem to have an important 
influence. This is most clearly marked in section 7, where the ex- 
perimental shelter was Spanish moss. At Victoria after about the 
12th of April more weevils emerged from this section than from all 
others combined. This effect was less marked in the other localities, 
but in each case there appeared to be a considerable delay in emer- 
gence, due to the nature of this shelter. Owing to the fact that this 
moss is living and growing while hanging in the cages or on the trees, 
it takes up moisture as no other class of shelter does. The evapo- 
ration of this moisture during the daytime then serves to keep the 
mass of moss cool, and it is a well-known fact that the temperature 
in bunches of this moss is several degrees lower than that of the air 
during the daytime. Undoubtedly the lower temperature in the 
moss is the factor which retards the emergence of the weevils so 
decidedly. This factor may also be considered responsible for the 
smaller activity of weevils shown in the moss sections during the 
winter. (See Table XXXI, p. G3.) 

A somewhat more detailetl statement of the emergence shows more 
plainly the peculiar manner in which this was distributed during 
1907. The figures are arranged for seven-day periods, and show the 
average temperature conditions prevailing as well as the percentage 
total of emergence occurring during each week. 

Table XLII. — Weekly sitimnanj of emergence records, shounng relation to effective tem- 
peratures, 1907. 



Date. 


Locality. 


Mean 
average 
ellective 
tempera- 
ture. 


Number 
of weevils 
emerged. 


Percent- 
age of 
total 
emer- 
gence. 


1907. 


rCalvert 


°F. 
30.0 
19.7 

24.7 
25. 7 
21.0 
30. 5 

30. 5 
27.0 
29.0 
30. 
33. 
32.5 
23. 

Ml 
28.8 
24.0 

31. 9 
24.9 
20. 
28. 7 
17.8 
13.0 
19. 
24.8 
lfi.3 
21). 3 


420 
848 
/ a 3f,3 
\ 481 
168 
413 
009 
228 
721 
549 
237 
504 
397 
128 
135 
147 
115 
194 
165 
134 
111 
127 
33 
44 
37 
58 
99 
2ti 


22 8 


Mar. 1-7 


1 Dallas 

Victoria 


24.5 




«12.0 




(Calvert 


15. 9 
9 1 


Mar. 8-14 


\ Dallas 


11 9 






90 3 




Calvert 


12 4 


Mar. 1.5-21 


•^Dallas 


20 8 




(Victoria 


18 




Calvert 


12.9 


Mar. 22-28 


•^Dallas 


14 




Victoria 


13.1 




Calvert 


7 


Mar. 29- Apr. 4 


•{Dallas 


4 




Victoria 


4 8 




Calvert 


6.2 


Apr. 5-11 


■^Dallas 






(victoria 


5.4 




(Calvert 


7 3 


Apr. 12-18 


■^Dallas 


3 2 




[Victoria. . . . 


4 2 




(Calvert 


1.8 


Apr. 19-25 


< Dallas 


1 3 






1.2 




(Calvert 


3 1 


Apr. 26-May 2 


{Dallas 

1 Victoria 


'> 9 




.86 



90317— Bull. 77—09- 



o- On February 28. 



82 



HIBERNATION OF THE COTTON BOLL. WEEVIL. 



Table XLII. — Weekly suminnry of emergence records, showing relation to elective tevi- 
■peratvrcs, 19U7 — Continued. 



Date. 


Locality. 


Mean 
average 
effective 
tempera- 
ture. 


Number 
of vi^eevils 
emerged. 


Percent- 
age of 
total 
emer- 
gence. 


1907. 


(Calvert.. . 


°F. 
26.4 
20.2 
29.3 
31.9 
24.0 
32.5 
35.5 
31.2 
31.8 
33.0 
23.3 
33.4 
30.7 
38.0 
30.9 
43.2 
38.0 
40.0 
37.4 
36.0 
36.8 
39.4 


113 

129 

50 

59 

121 

26 

54 

103 

17 

49 

20 

8 

30 

13 

21 

10 

5 

2 

5 

4 

1 

1 


6.1 


May 3-9 


mallas 


3.7 




[victoria . . . 


1.6 




(Calvert 


3.2 


May lO-li. 


pallas 

(victoria 


3. 5 




.86 




(Calvert 


3.0 


May 17-'':; 


l' Dallas 


3.0 




[victoria 


.56 




iCalvert 


2.6 


May 24-30 


] Dallas 


.6 




(victoria . 


.20 




(Calvert 


1.6 




■^Dallas 


.4 




1 Victoria 


.7 




(Calvert 


.5 


June 7-13 


•^Dallas 


.15 




(victoria. 


.07 




(Calvert 


.3 


June 14-20 


.^Dallas 


.12 




(victoria 


.03 


June 21-27 


(Calvert 

.^Dallas 


.01 




(victoria 





Total emergence: 

Calvert 1 ,S42 

Dallas 3 , 464 

Victoria 3,026 

Grand total 8,332 

The large percentage of total emergence occurring during the fii'st 
week of March is very striking and unquestionably also very excep- 
tional. Only the extremely high range in temperature can explain 
this unusual record. Taking the average of the three locations, 
practically one-fourth of the total emergence occurred during the 
first week of March. During the following two weeks more than 
another one-fourth also emerged. During this period the tempera- 
tures averaged as high as they do ordinarily in May; and owing to 
the fact that a considerable majority of weevils had left shelter 
before the end of March the number emerging after that time shows 
a marked decrease. 

It must not be supposed that these statements represent anything 
like usual conditions, although they unquestionably represent the 
facts in regard to emergence in 1907. The comparison of these 
records with those for Dallas and Keatchie (see p. 44) in 1906 will 
show clearly the exceptional nature of the variation. 

It should be stated that when the emergence takes place as rapidly 
as was the case in March, 1907, the actual number of hving weevils 
in the field may be expected to increase for some time because of the 
fact that a larger number of weevils is atlded to the total living on 
account of continued emergence than is lost on account of death 
among weevils which have previously emerged. 



LONGEVITY OF WEEVTLS AFTER EMERCiENCE. 83 

LONGEVITY OF WEEVILS AFTER EMERGENCE FROM 
HIBERNATION. 

Precedino; records have shown that on tlie average the weevils sur- 
viving:; hil)ernation had hved for over five months before their emer- 
gence. It is impossible to determine even approximately how old 
weevils may have been at the time they were placed in the hiberiui- 
tion cages. The longevity records here, shown must, therefore, be 
very conservative. They may indicate very closel}^ the average 
length of life of weevils which survive hibernation, but shouhl not be 
considered as showing actually the maximum longevity. It has 
seemed advisable, therefore, to base the studies upon longevity after 
emergence from hibernation, since the exact dates for emergence and 
for deaths have been carefully determined. 

As the weevils were collected daily from the cages, those found at 
each date must have emerged practically upon that date. It was 
the general practice to divide the weevils from each section of the 
cage into two lots of approximately equal numbers, one lot being 
placed in a series in which they received no food and the second lot 
being placed in a series which was supplied wdiatever stage of cotton 
was then available to weevils in the field where the experiments were 
being made. Thus, early in the season at Dallas, all weevils were 
necessarily placed in unfed series, since no cotton existed in the field. 
In each locality the first food consistetl of tlie tender leaves of volun- 
teer or sprout plants. As soon as squares were formed in the field 
these were supplied to the weevils in the fed series of experiments. 

An a general rule the weevils emerging upon three consecutive 
days were placed in a cage bearing the same series designation, and 
the average date of emergence was considered as applying to the 
entire lot. This arrangement was necessary to reduce the amount of 
w^ork required in caring for so many cages as would be needed to 
keep each day's weevils entirely separate. 

In both the fed and unfed series frequent examinations were made 
to determine the time of death of each weevil, and fresh food was 
supplied to weevils in the fed series. Upon the death of a weevil 
its sex was tletermined and its period of life after emergence was also 
recorded. The manner in which sex can be positively determined is 
described in succeeding paragraphs. (See p. 91.) In this way the 
records for each lot bearing a serial number were kept by themselves 
and the results for each series are comparable with all others. While 
it would be most significant to present the records in the form of a 
summary of each series which would allow these comparisons to be 
seen, the necessity for abridging the tabular matter, so far as may be 
possible, prevents our doing so. Therefore for both the "unfed" 
and for the "fed" experiments we can give only the grand totals 
and averages with general statements based upon the tabular studies 
from which these figures are obtained. 



84 



HIBEKNATION OF THE COTTON BOLL WEEVIL. 



LONGEVITY OF UMFED WEEVILS AFTER EMERGENCE FROM HIBERNATION. 

Since the diuation of life of unfed weevils was so much shorter 
than for fed weevils, the records of the former will be considered 
first. The principal object in the experiments with unfed weevils 
was to determine the time whicli they might survive while waiting 
for the growth of a food supply in the spring. The results have a 
most important special l)earing upon the advisability of hastening 
or deferring Ihe time of planting of cotton, especially when considered 
in connection with the period of emergence from hibernation. The 
figures given are based upon completed records only, all partial 
records having l)een discarded. 

Table XLIIL — LoiKjcrihi of inifcd irccvils uflo- nuny/riicr from liihcrnatioti, 3farc}i 

io .Inly, lixn . 





Number 

of series 

1.e.st,ecl 

unfed. 


Total 
weevils 
emerged. 


Weevils in series lots. 


Maximum life. 


Average duration of life. 


Locality. 


Total. 


c? 


9 


c? 


? 


c? 


9 


Both 
sexes. 


Texas: 

Cal\-ert 

Dallas 

Victoria 


19 
17 


1,085 
2,317 
1,418 


1,079 
2,179 
1,300 


585 

1,178 

875 


494 
1,009 

485 


Days. 

48 
90 
44 


Days. 

26 
88 
40 


Days. 

■ 8.05 

13.00 

8.00 


Days. 

8.09 

11.09 

7.40 


Days. 

8.07 
12.50 
8.20 


Total and 
average . 


61 


4,820 


4,618 


2,638 


1,988 


90 


88 


10.30 


9.80 


10.10 



The records both for maximum ami average duration of life are very 
importalit. In the record showing maximum and average duration 
of life for- each sex in each locality the time at Dallas exceeds by 50 
per cent the time at either Calvert or Victoria. It should be stated 
that when weevils are kept in confinement it is probal)le that the most 
fav()ral)le conditions which can be furnished them can hardly be siip- 
pos{^d to prohmg their life beyond the noi'mal condition in the field. 
Any unfavorable conditions in the cages will shorten the period. It 
was found in the course of the work that whenever sunshine was 
allowed to strike directly on the lantern globe breeding jars in wliich 
the weevils were foi- the most part confined, the heat and excessive 
humidity generated within the globe caused an abnormal activity 
among the weevils, and if prolonged or frequently repeated, it 
resulted in their early death. It was also found that in the breeding 
cages among tlie unfed weevils the degree of moisture was less than 
would normally occur on plants or at the surface of the ground in the 
field. Tliis dryness also naturally shortens the Hfe of weevils. In 
an experiment at Dallas series 14 was kept with plenty of moisture 
while series 15 was dry. Otherwise conditions in the two series were 
identical. The average life in the wet series was 20.3 days while in 
the dry series it was but 7.1 days. Other experiments pointed to the 
same conclusion. 



LONGEVITY OF WEEVILS AFTER EMERGENCE. 85 

These facts indicate that the records for Calvert and Victoria are 
probably considerably below the normal survival period for emerged 
weevils in the field, and the records for Dallas are at least conserva- 
tive. The difference in duration of life between the males and 
females was but slight, but rather luiiformly in favor of the males. 
In each locality the maximum longevity was shown l)y males. This 
fact agrees with previous conclusions regarding the relative duration 
of life of the two sexes. Apparently copulation does not materially 
affect the longevity of eitlier sex. In this connection it may be 
stated that unquestionable instances of mating were found among 
weevils immediately after their emergence and liefore there was any 
possibility of their having fed. This was of rare occurrence, and the 
question of fertility resulting was not positivel}- determined. 

From the records it becomes evident that many emerged weevils 
may survive from six to twelve weeks without food and that the 
average survival for all weevils may be lietween one and two weeks. 

There is some evidence to show that it is possible for these unfed 
weevils to move rather extensively in seai'ch of food, and undoubtedly 
this is done in many instances. Other observations, however, indi- 
cate that if food is not found in the vicinitv of emero-ence the weevils 
may become quiet foi- a considerable period before again seeking food, 
and in this way their movement may occur only through compara- 
tively short distances. It is also probable that when they hrst find 
a food supply they do not intentionally leave it in searcli of other 
plants which may be in a more advanced stage of growth. 

As to the proportion of each sex among the weevils suiviving in 
these experiments it appears that 57 per cent were males. The maxi- 
mum longevity of any weevil was ninety days. This was a male 
which was kept under outdoor conditions from March 1, when it 
emerged, to May 30, when it died. The maximum life for a female 
was eighty-eight days. This weevil emerged April 25 and died July 
20. The average temperature under which this lot of weevils was 
kept ranged between 45 and 60 degrees and the average length of life 
for all of the 55 weevils tested in series 17 at Dallas was slightly more 
than thirty days. This emphasized the important effect of tempera- 
ture upon the period of survival without food. 

The grand total for average duration of life shows 10.1 days for 
more than 4,600 weevils. The males lived on an average one-half 
day longer than did the females. 

It would be both interesting and valuable if the records showing a 
summary of the results for each sex in each ^series of experiments 
could be presented in full. It is thought, however, that the corre- 
sponding records for the fetl weevils have a greater value and it may 
be allowable to present in place of the full records for the unfed 
weevils merely a brief statement of the most important facts as to 
the survival of each sex. 



86 



HIBERNATION OF THE COTTON BOLL WEEVIL. 



The most apparent fact is that there is a consistent increase in 
duration of hfe without food in both sexes in a northern locahty, as 
at Dallas, as comj)ared with a southern locality, as at Victoria, while 
Calvert occupies an intermediate })osition both in the starvation 
period and geographically. Lower temperatures are obviously directly 
correlated to the degree of activity of the insects and thus determine 
directly the limit of endurance without food. But in no case is there 
any very marked variation between the sexes in the same locality. 

It appears tliat practically two-thirds of all weevils died during 
the first ten days after their emergence. One-fourth of the total num- 
ber tested lived to between eleven and tw^enty days. Beyond twenty 
days the percentage surviving becomes comparatively small, and 
between fifty and ninety days the percentage for each ten-day 
period is rather surprisingly uniform. It is very evident, however, 
that even in a season when the bulk of emergence may occur as 
unusually early as it did in 1907 it would be absolutely impossible 
to exterminate the weevil by any ]5()ssible (Uday in the time of plant- 
in<r cotton. 



LONdEVITY OF FED WEEVILS AFTER EMERCiENCE FROM HIBER- 
NATION. 

The records indicating the longtndty of weevils which were fed 
after their emergence from hibernation have been prepared in a 
similar way to show results comparable with those for unfed weevils 
which have just been given. They form the second part of the com- 
parative series of experiments to determine longevity. The condi- 
tions of food supply, while kept as favorable as was possible, could 
not at best equal the natural conditions in the field, although the 
weevils were evidently saved the trouble which they might have 
experienced in the field of finding their first food supply. The con- 
siderations which have previously been mentioned in regard to the 
effect of high temperature and excessive moisture in the jars when 
exposed to sunshine ap])ly with fully as much force to the fed as to 
the unfed series of experiments. 

Table XLIV. — Longevity of vecvils fed after emeryenee from hibernation, March to 

September, 1907 . 



I.ocality. 


Number 

of series 

tested, 

fed. 


Total 
weevils 
emerged. 


Number of weevils in 
series. 


Maxhuum life. 


Average duration of life. 


Total. 


c? 


9 


c? 


9 


3 


9 


Both 
sexes. 


Texas: 

Dallas 

Calvert 

Victoria 


7 
26 
20 


998 

740 

1,450 


901 

715 

1,349 


490 
363 

785 


411 
352 

564 


130 
92 

84 


108 
118 
86 


38.4 
29.2 
1.5.1 


38.0 
30.7 
14.2 


38.2 
30.0 
14.7 


Total and 
average . 


53 


3,188 


2,965 


1,638 


1,327 


130 


118 


25.2 


25.9 


25.5 



LONGEVITY OF WEEVILS AFTER EMERGENCE, 87 

Only about two-thirds as many weevils were carried through in 
the fed tests as in the unfed tests. Among the total of 2,965 weevils 
55 per cent were males, while in the unfed experiments 57 per cent 
were males. The average duration of life shows but very sUght 
variation between the sexes, both living between twenty-five and 
twenty-six days. This average is somewhat smaller than has pre- 
viously been obtained in similar experiments, and this is probably 
due to the greater exposure to sunshine of the cages in which the wee- 
vils were kept in this series of experiments. The average period of 
life with food was about two and one-half times that without food. 

Among the fed weevils, as among the unfed, the longest life occurred 
at Dallas. This also was a male weevil which emerged from hiberna- 
tion on May 6 and survived until September 13, or one hundred and 
thirty days. The greatest length of life for a female occurred at Cal- 
vert. This weevil emerged on April 11 and died on August 7, having 
been active one hundred and eighteen days. 

The full length of life of the last weevil d.ying in these experiments 
is also a matter of interest. This weevil was collected in the field at 
Dallas and placed in the hibernation cage on October 16, 1906. 
From that time until May 6, 1907, it had no food. The period from 
its collection until its death lacked but a day or two of being eleven 
months, during three-fifths of which period it existed without food. 
This is next to the longest lived boll weevil of which we have record, 
the longer record being slightly more than eleven months in the case 
of a male weevil hibernated at Victoria in 1903. 

In a study of the emergence movement and of the duration of life 
of fed weevils by ten-day periods we have used the total number of 
weevils of each sex observed in each locality as the basis upon which we 
have determined the percentage of mortality occurring in each succes- 
sive ten-day period. The full records for each locahty have been 
omitted and only the totals for each sex in each locality have been 
included in Table XLV (p. 88). The emergence from liibernation was 
distributed through four months, or slightly more, in 1907. A study 
of the omitted records shows that, as a rule, the weevils living longest 
emerged at approximately the middle of the emergence movement. 
It is probable that these weevils were among those which entered 
hibernation at the most favorable period during the preceding fall 
and that they found also the most favorable class of shelter conditions 
to protect them during the winter. The importance of breaking up 
this succession of conditions, so favorable to the sur^^val of weevils, 
their maximum length of life, and, consequently, their greatest inju- 
riousness, need only be mentioned to be appreciated. That early 
fall destruction of stalks, the cleaning up of rubbish which might 
shelter weevils most favorably during the winter, and the early 
planting and uniform planting of the crop are all logical ])arts or steps 



OO HIBERNATION OF THE COTTON BOLL WEEVIL, 

in the rational method of fighting- tlie boll weevil is j)lainly shown by 
these studies. 

Table XLV. — ('nnipnriso)!. of fnivniiarics for longevity (ffcd ivcrvUs. hij ten-day periods, 

in. eacli locality. 

MALE WEEVILS. 





Numltcr 
of weevils 
in series. 


Weevils dying within a period of — 


Locality. 


1-10 days. 


11-20 days. 


21-30 days. 


31-40 days. 


41-50 daj^s. 


51-60 days. 




Num- 
ber. 


Per 

cent. 


Num- 
ber. 


Per 

cent. 


Num- 
Iier. 


Per 

cent. 


Num- 
ber. 


Per 
cent. 


Niun- 
ber. 


Per 

cent. 


Num- 
ber. 


Per 
cent. 


Dallas 


490 
303 

7.S5 

1, 038 


47 

80 
371 


9.0 
23.8 
47.3 


72 

01 

210 


14.7 
10.9 
27.6 


87 
00 
110 


17.7 
16.7 
14.8 


08 
50 
39 


13.9 
13.8 
5.0 


87 
49 
14 


17.7 

13.5 

1.8 


47 
41 
13 


9.0 

11.3 

1.7 


(^ahcfl 


Victoria 


Total and 
average . 


504 


30.2 


349 


21.3 


203 


10.0 


1.57 


9.0 


1.50 


9.2 


101 


6.2 



FEMALE WEEVILS. 



Dallas 

Calvert 


411 
3.52 

504 


32 

67 
293 


7.8 
18.8 
51.9 


54 
63 
133 


13.1 
17.7 
23.5 


91 
60 

88 


22. 1 
16^7 
15.6 


46 
58 
24 


11.2 

16.3 

4.3 


91 
54 
11 


22.1 
15.2 
2.0 


37 
32 
10 


9.0 
9 


Victoria 


1.8 


Total and 
average . 


1,327 


392 


29.5 


250 


18.8 


239 


18.0 


128 


9. 6 


150 


11.7 


79 


5.9 



WEEVILS OF BOTn SEXES. 



Total and average, 2,967 . . . 



890 30.2 


599 


20.2 


502 


16.9 


285 


9.0 


300 


10.3 


180 



MALE WEEVILS. 





Number 
of weevils 
in series. 


Weevils dying within a period of— 


Locality. . 


01-70 days. 


71-80 days. 81-90 days. 


91-100 days. 


Over 100 

days. 




Nimi- 
l)er. 


Per 
cent. 


Num- 
l)cr. 


Per 
cent. 


Nimi- 
l)er. 


Per 
cent. 


Nimi- 
ber. 


Per 
cent. 


Num- 
ber. 


Per 
cent. 


Dallas 


490 
303 

785 


30 
7 
4 


7.3 

1.9 

.5 


31 

6 
8 


0.3 
1.7 
1.0 


5 
2 

3 


1.0 7 

1.0 2 

.4 


1.5 
.6 


2 



0.4 


Calvert 
















Total and 
average . 


1,638 


47 


2.9 


45 


'2.8 


10 


.6 


9 


.6 


2 


.1 



FEMALE WEEVILS. 



Dallas 

Calvert 


411 
352 
564 


32 
9 
4 


7.8 

2.5 

.7 


22 
3 
1 


5.4 
.8 
.2 


4 
5 

1 


1.0 

1.4 

.2 


1 
2 



0.2 

.6 


1 
1 



0.2 
.3 


Victoria 




Total and 
average. 


1,327 


45 


3.4 


26 


2.0 


10 


.8 


3 


.2 


2 


.1 



WEEVILS OF BOTH SEXES. 



Total and average, 2,965. 



92 


3.1 


71 


2.4 


20 


0.7 


12 


0.4 


4 



0.1 



LONGEVITY OF WEEVILS AFTER EMERGENCE. 89 

At Dallas the number of weevils surviving for two months or 
more amounted to 15. G per cent of the total number observed. Prac- 
tically 50 per cent of each sex survived for more than six weeks. 

At Calvert 15 per cent of the total number of weevils survived 
over fifty days and 50 per cent for more than thirty days. The 
average life at Calvert was nearly ten days less than at Dallas. It 
is very noticeable that those weevils which lived longest at Calvert 
emerged chning about the middle of the emergence period. The 
weevils which were very late in emerging survived for only a short 
time. The decrease in the percentage of survival is markedly regular 
from the first ten days to the end of the period. The most decided 
decrease occurs between sixty and seventy days. 

The maximum longevity at Victoria fell considerably short of 
that at Calvert and Dallas. In this case 15 per cent of the weevils 
survived beyond only about twenty-five days and nearly 50 per 
cent died during the first ten days. The reason for the marked 
shortening of life at Victoria was undoubtedly the greater exposure 
to sunshine of the jars in which the weevils were confmed. 

This comparison shows that length of life uniformly averages 
lono-er in northern Texas than in either central or southern Texas. 
At Dallas 3 weevils, at Calvert 1, and at Victoria none lived more 
than one hundred days. At Dallas 11 weevils, at Calvert 5, and at 
Victoria none lived more than ninety days. From the grand sum- 
mary of the records in both sexes it appears that among approxi- 
mately 3,000 weevils 50 per cent died during the first twenty days. 
Two-thirds of them died in the hrst thirty days and three-fourths of 
them in the first forty days. 

From these records it appears that any kind of a food supply will 
serve to maintain a majority of the emerging weevils for more than 
three weeks. This consideration has a special significance in southern 
Texas, where sprout and volunteer cotton usually occur. This sub- 
ject will be further considered in the relation of hibernated weevils 
to food supply. 

BEARING • OF OBSERVATIONS ON FEU AND UNFED WEEVILS ON THE 
POSSIBILITY OF AVOIDING DAMAGE TO COTTON BY LATE PLANTING. 

One of the most important features of the experiments on the long- 
evity, with and without food, of weevils that have survived the 
winter, is the bearing that the results have on the theory of late 
planting of cotton to avoid damage. This theory has been pro- 
pounded by numerous persons ever since 1895. 

In the series of experiments with unfed weevils 4,600 individuals 
were used; in the series with fed weevils 2,965. The unfed series is 
the more important with reference to late planting, The maximum 
length of life of the unfed weevils emerging in February, 1907, was 



90 HIBERNATION OF THE COTTON BOLL WEEVIL. 

14 days; the average 6.9 days. The maxinmm of the individuals 
emergino; in March was 51 days; the average 16.9 days. For the 
April-emerging weevils the maximum was 46 days; the average 21.2. 
For the May-emerging weevils the maximum 33 ; the average 15.8 days. 
Of the June-emerging weevils maximum 12 <hiys; the average 7.4. It 
will be seen that even in such an abnormal season as 1907 weevils 
emerging any time during the month of ]\Iay might be expected to live 
for at least 15 days and individuals emerging at any time during the 
month of June to live for more than 7 days. It is thus clear that many 
weevils emerging in May would survive without any food whatever 
until considerably after the middle of pJune and that those of the June 
emergence would survive in many cases beyond the first of July. 

It is important to note that a considerable percentage of the 
emerging weevils did not appear until late. For instance, 10.2 per 
cent of all the weevils which survived at Calvert did not appear 
until between May 10 and June 6. At Dallas the percentage for this 
period was 7.5, and at Alctoria, 2. 38. 

The observations on the longevity of the fed weevils also has a bear- 
ing on late planting, since there is always some volunteer cotton 
around seed houses and elsewhere that will be found by the weevils. 
The maximum length of life of the fed weevils which a])peared in 
February was 47 days, the average 45 days; of Ahirch-appearing 
weevils the maximum 93 days, average 45.5 days; of April-appearing 
weevils maximum 82 da^^s, average 46.5 days; of J\f ay-appearing 
weevils maximum 86 days, average 5.5 days; of June-appearing 
weevils maximum 46 days, average 37.8 days. 

The longevity of the weevils emerging in May and June is most 
important. The average survival of 55 days in one case and the 37.8 
in the other shows that with such food as can easily be obtained, at 
least some of the emerging weevils would be carried over until far 
into the summer, even if no cotton were planted. 

The records just referred to are, of course, a sufficient refutation of 
the theory that the weevil could be "starved out" by late planting. 
It has been proposed, however, that the number of weevils surviving 
to damage late-planted cotton would be relatively so small that such 
cotton would have a better chance to mature a crop than that planted 
earher. In order to test this matter the Bureau of Entomology has 
conducted practical field tests in which cotton has been planted 
about the 10th of June. In one season four of these experiments were 
performed in parts of Texas showing distinct climatic features and one 
in Louisiana in cooperation with the State Crop Pest Commission. In 
every case the yield was cut down so severely by the weevils that 
survived the prolonged period in which no cotton was to be found 
that the impossibility of producing cotton in that way was fully 
demonstrated. 



SEX OF WEEVILS SURVIVING HIBERNATION. 



91 



SEX OF WEEVILS SURVIVING HIBERNATION. 

We found it possible to reailily and accurately recognize male and 
female weevils without a partial dissection. In comparatively few 
species of weevils are the males and females so closely similar in gen- 
eral external character as in the case of the Mexican cotton boll 
weevil. It was found that size depended primarily upon the food 
supply of the larva and that it had no special significance in regard 
to sex, although it appears that the average male is slightly smaller 
than the average female. There exists a rather wide variation also 
in coloration, which also proved to depend upon food suppl}^ and 
age rather than upon sex. 

SECONDARY SEXUAL CHARACTERS. 

We are indebted to Dr. A. D. Hopkins, of the Bureau of Ento- 
mology, for indicating the most strongly marked points of difference 
in the secondary sexual characters of the boll weevil. The distinctive 



6 





u 



^ ^pyG/D/UM-- " " 8 



(^length 38mm.; tip fo/nser/'/on /2mm. 
Q >^ 42 7? 7) » >? /8 " 



Fig. 9.— Secondary sexual eharavters of Antlionomus gravihs. (After Ilopkins.) 

characters (see fig. 9) are found upon the snout and upon the dorsal 
side of the last two alxlominal segments, which are normally almost 
completely hidden by the wing covers. The differences are subject to 
some variation but are still sufficiently constant to enable a close 
observer to positively separate males from females with the aid of a 
hand lens. Since these points of distinction have not previously 
been published it seems advisable to include them here, as they fur- 
nish the basis for the determinations of sex which follow. 

Female. — The snout of the female is slightly longer and more 
slender than that of the male. It usualh^ tapers slightly from each 
end toward the middle when viewed from above. The antennae 
are inserted slightly farther from tlie tip than is the case in the male. 
The insertion is at about two-fifths of the distance from the tip of 
the snout to the eyes. As a rule the surface of the snout is more 
smooth and shining than in the male. A slight depression, rather 
elongated and much larger than an}' of the other punctures upon the 



92 



HIBERNATION OP THE COTTON BOLL WEEVIL. 



snout, occurs between the bases of the antenna. When the wing 
covers and wings are unfolded tlie abdomen shows seven distinct 
dorsal segments. Tlie last segment visible from above in the female 
is called the propygidium. In the female this covers the terminal 
segment or pygidium, which can be seen only from the sides. 

Male. — wSnout slightly shorter, tliicker, and more coarsely punctured 
tlian in the female. The depression mentioned in thefemale is lacking. 
The antennae are inserted at practically one-third of the distance from 
the tip of the snout to the eyes. The sides of the snout are very 
nearly parallel. In the abdomen the male shows eight distinct dorsal 
segments, the terminal segment (pygidium) not being covered by the 
propygidium as is the case in the female. 

In general practice an examinaticm of the snout is sufficient to 
determine the sex of each weevil. 

PROPORTION OF SEXES SURVIVING HIBERNATION. 

The records here given as to the proportion of sexes surviving 
hibernation are confined to determinations of sex for positively 
hil)ernated adults. 

Table XLVI. — Sex ofivranh surviving hihernation in Texas. 



Year. 



1903.... 

1904 

1904.... 
1904. . . . 
1906.... 
1907.... 
1907. . . . 
1907.... 



Locality. 



Several places 

Calvert 

Victoria 

do 

do 

Dallas 

Calvert 

Victoria 

Total and average 



Male. 



Number 
deter- 
mined. 



2(i9 

40 

42 

Ifil 

84 

1,008 

948 

1,600 



4,872 



Percent- 
age of 
total ex- 
amined. 



Female. 



Number 
deter- 
mined. 



174 
27 
21 
132 
57 
1,412 
846 
1,049 



3,718 



Percent- 
age of 
total ex- 
amined. 



39.3 
40.0 
33.3 
45.0 
40.4 
45.8 
47.0 
38.7 



o Weighted average. 

While these records show considerable variation in the proportion 
of the sexes for different localities and during different seasons, there 
is a uniformity in the general preponderance of males. In the total 
of 9,000 weevils examined 53.6 per cent were males. This proportion 
corresponds quite closely to that found to exist among weevils enter- 
ing hibernation (see pp. 16-17). It is evident, therefore, that the pre- 
ponderance of males in the spring is not due to any superior power of 
endurance enabling them to hibernate more successfully than females. 
Apparently there is little, if any, difference in respect to the ability 
of the two sexes to hibernate successfully. 



RELATION OF HIBERNATED WEEVILS TO FOOD SUPPLY. 93 

From a knowledge of the habits of the aduhs it appears that the 
preponderance of males in the spring is a favorable ]:»r()vision of natm-e, 
making it more certain for the sexes to mate and to insure reproduc- 
tion. In spite of a number of attempts to obtain a definite answer 
to the question whether it is absolutely necessary for copulation to 
occur in the spring before females can reproduce, this point has not 
been positively settled. There are indications, however, that in most, 
if not all, cases this is essential. The fact that mating occasionally^ 
occurs immediately after emergence but before either sex has fed in 
the spring has previously been noted. Unfertilized females at any 
season of the year deposit nearl}- all of their eggs upon the outsitle of 
squares or bolls, where they C|uickly dry up. No sign of partheno- 
genesis has been found. The meeting of males and females is to a 
large degi'ee accidental, and during a season when weevils are com- 
paratively scarce it is likely that in very inan}^ cases the sexes fail to 
come together or the meeting may be delayed for a considerable 
period. 

Experiments have shown that the male weevils do not actively seek 
the females. They seem to recognize their presence through a dis- 
tance of hardly more than an inch. The meeting of the sexes depends 
therefore largely upon their coming into close proximit}^ upon a cot- 
•ton plant. Since the males are less active in their movement than are 
the females, the value of the existence of a majority of males be- 
comes apparent. The larger number of males and the more active 
habits of tlie females serve to increase the chances for the meeting 
of the sexes in the spring without materially decreasing the power 
of multiplication of the species. 

RELATION OF HIBERNATED WEEVILS TO FOOD SUPPLY. 

The relation of hibernated weevils to food supply is an important 
subject, since the reproduction and multiplication of the species de- 
pend primarily upon this point. As has been sliown in numerous 
places the emergence peiiod of the weevil practically coinci(k^s with 
the average period in the planting of cotton. The long duration of 
emergence makes it practically impossil)le to secure the planting of 
the entire crop either earlier or later than the emergence period of the 
weevil. It has been found both from the study of the weevil and from 
large-scale experiments in the culture of cotton that during nearly 
every season there is a decided advantage in planting the crop as 
early as soil and climatic conditions may permit. Too much empha- 
sis can not be placed upon the fact that, at whatever time the cotton 
in a locality may be planted, there will be a decided advantage in hav- 
ing it all planted at as near a uniform date as is possible. It is obvious 
that this will entirely prevent the development of weevils until prac- 
tically all of the crop begins fruiting. In this way the fruiting of the 



94 HIBERNATION OF THE COTTON BOLL WEEVIL. 

plant may take place most rapidly during the period of development 
of the first and second generations of weevils. 

Early planted fields, although they may serve to attract, in some 
small degree, the weevils from surrounding fields, will almost invariably 
produce larger yields than later planted fields in the same locality. 
The reason for this is, primarily, the longer period which intervenes 
between the beginning of setting fruit with its coincident reproduction 
of weevils and the time when maximum infestation of the field occurs. 
Comparatively few weevils appear to move from one field of cotton to 
another until after maximum infestation takes place. 

Repeated experiments in deferring the planting time of cotton have 
invariably resulted in small and comparatively unprofitable crops. 

Extended observations made during the spring of 1906 showed that 
volunteer" cotton occurred very commonly in fields and yards, along 
roadsides, and around ginneries and seed houses in every one of the 
seventeen localities examined about the midtUe of May, representing 
territory then infested by the weevil and also extending outside the in- 
fested territory into Mississippi, Arkansas, and Tennessee. This makes 
it practically certain that volunteer" cotton occurs everywhere 
throughout the cotton-growing area, and it may therefore liave con- 
siderable significance in supplying emerged weevils with their first 
food in spring. 

Extensive examinations have also shown that sprout" cotton com- 
monly occurs throughout the southern lialf of the weevil-infested area 
in Texas during the average season. As a rule the development of 
tliis takes place several weeks in advance of the average planted cot- 
ton, and it becomes therefore a very important factor in maintaining 
hil)ernated weevils and in the development of their first progeny. 
Ahhough attention has repeatedly been called to this fact, large quan- 
tities of sprout cotton are still allowed to grow unchecked. It is 
doubtful whether it is advisable to cultivate this even where it 
amounts to half a stand. Wherever scattering plants occur in a field 
of planted cotton they should certainly be chopped out as (piickly as 
they occur. The profit to be derived from them is nothing when com- 
pared with the great damage which their presence may inflict upon 
the remainder of the crop through providing the earliest opportunities 
for the reproduction and multiplication of the weevils. 

a The term "volunteer" is restricted to that class of cotton coming from the acci- 
dentally scattered seed of a preceding crop. S|)r()ut cotton, also called stubble or 
seppa cotton, is a sprout growth from old cotton roots occurring during the winter or 
subsequent spring. 



SUMMARY AND CONCLUSIONS. 95 

SUMMARY AND CONCLUSIONS. 

Hibernation is the term used to desio;nate those phases in the hfe 
antl seasonal history of the boll weevil (or of any other animal or 
plant) which are concerned with its existence through the winter and 
the manner in which the species is protected or maintained in passing 
from one season to the next. Food, climatic, and slielter conditions 
are the principal factors concerned in hibernation. 

Food conditions in the fall govern largely the abundance of indi- 
viduals which may enter hibernation and therefore affect the abun- 
dance of the species in the following spring, since climatic and shelter 
conditions govern largely the proportion of the hibernating individ- 
uals which may survive. 

A large majority of the weevils developed in a field during the 
season are produced from squares. 

Weevils becoming adult comparatively late in the season are more 
likely to survive hibernation than are those which have been active 
for a number of weeks before the time arrived for them to hibernate 
successfully. 

It is possible that offspring of each of the four or five generations 
which are produced on the average may survive to enter hibernation. 

No "top crop" can reasonably be expected within the weevil- 
infested area. 

All stages of the weevil may enter hibernation ami under excep- 
tionally favorable climatic conditions larvas which are more than half 
grown may complete their development if in bolls and become mature 
during the hibernation period. Immature stages in squares rarely 
survive. Nearly all of the weevils surviving were adult before the 
beginning of the hibernation period. 

The destruction of stalks in the fall, as long as possible before the 
normal hibernation time, is the most economical and effective method 
known for reducing the number of weevils entering hibernation. 

"Entrance into hibernation" denotes the beginning of the generally 
inactive period, but it does not necessarily imply a change of position 
for the individuals involved. For the species and often also for the 
individual it is a gradual process depending primarily upon tempera- 
ture conditions. The duration of the entrance period for the species 
depends upon the severity of the drop in temperature below about 
43 degrees of mean average temperature. This period usually occurs 
coincidently with the first killing frosts and extends through a period 
of about twenty-five chn's. 

From close examination of 1,750 weevils it seems that about 60 
per cent of those entering hibernation are males. 

The number of weevils per acre or per plant which may enter hiber- 
nation depends especially upon preceding climatic and food conditions 



96 HIBEENATION OF THE COTTON BOLL WEEVIL. 

and has been found to vary in different seasons and localities, occa- 
sionally being as high as 50,000 weevils per acre, or an average of from 
7 to 10 weevils per plant. An average of the results in 17 of the 
most carefully studied fields shows 8,552 weevils per acre, or slightly 
more than 1 weevil per plant. 

The proportion between the numbers of weevils hibernating on the 
stalks and among rubbish scattered on the surface of the ground 
changes as the season advances, the number on the stalks decreasing. 

Great mortality occurs soon after the weevils enter hibernation, 
especially among those upon the surface of the ground. 

Hibernation usually takes place as the mean average temperature 
falls below 55 degrees and may remain complete until the mean 
temperature rises above 60 degrees. 

Weevils may avail themselves of almost any kind of shelter, and 
the favorable character of the shelter in relation to prevailing cli- 
matic conditions will influence the percentage of survival. Many 
pass the winter sheltered by the old bolls that remain hanging upon 
the stalks. The percentage of survival in bolls decreases generally 
from southern to northern Texas. Bolls are frequently so important 
a factor in shielding weevils from one season to another that it is 
advisable to destroy them as a regular practice even in northern 
Texas. 

Exceptionally cold and wet winter weather is most unfavorable for 
weevil survival. The destruction of possible shelter througli clean 
culture in the fall is an effective way of reducing weevil injury to the 
following crop. The shelter to be found in timber fringes around 
cotton fields is much more difficult to remove or control than is that 
within the fields. The importance of such unavoidable conditions 
may be minimized by judicious cleaning up and by rotation of crops. 

Occasionally weevils may survive in stored cotton seed and be dis- 
tributed along with it at planting time. This fact justifies the main- 
tenance of quarantine regulations against the free movement from 
infested to uninfested territory of cotton seed and closely related 
cotton products which are apt to shelter weevils. 

Most of the information obtained in regard to the hibernation of 
the weevil has resulted from cage experiments in which the influential 
conditions could be separated and to some degree brought under 
control. 

During the winter of 1902-3, at Victoria, Tex., in the small-cage 
experiments with 356 weevils, an average of about 11 j)er cent sur- 
vived. During the following season, also at Victoria, among 400 
weevils but one-fourth of 1 per cent survived. During the winter of 
1004-5 larger numbers of weevils were under observation at each of 
six localities ranging from the southern to the northern portions of 



SUMMARY AND CONCLUSIONS. 97 

the infested area. This was the season of most exceptional rainfall 
and cold, and it was not surprisino; that no w^eevils survived in the 
cage tests except at Victoria, which was the southernmost point 
of experiment. An averao;e for the six localities shows a survival of 
less than two-thirds of 1 per cent. In the small-cage work of 1005-6 
there was an average survival of 1.3 per cent, and practically all of 
this occurred in the outdoor cages. 

The most important work done in 1905-6 was in a large cage at 
Keatchie, La., where 25,800 weevils w^ere placed in 18 compartments. 
The survival in this cage was 2.82 per cent, and the emergence oc- 
curred between March 22 and June 28, 1906. The cages having 
nearest to the ordinary field conditions with poor cultivation gave 
the largest percentage of successful hibernation. A study of the 
emergence and temperature records for similar experiments at Dallas, 
Tex., and Keatchie, La., shows that at the former place approximately 
50 per cent of the emergence occurred while the temperature ranged 
between 58 and 68 degrees, while at the latter place one-half of the 
total emergence took place while the temperature ranged betw^een 
about 65 and 75 degrees. Very few weevils emerged while the tem- 
perature w^as below 57 degrees. 

There is an optimum period for entrance into hibernation, and 
w^eevils entering tkiring this period have a considerably better chance 
of surviving than do those which enter either earliei- or later. If 
hibernation is begun earlier than this optimum period, it is likely that 
emergence will be completed earlier during the following season, and 
also if entrance occurs later than this period it is likely that emer- 
gence wdll begin imusually early in the following spring. 

Variation in the period of entrance into hibernation and the dif- 
ference in the nature of the shelter secured by the weevils may rea- 
sonabh' account for the variations found in the amount of accumu- 
lated effective temperature recpured to produce complete emergence 
in the spring. 

Weevils emerging earlier in the season survived for a longer period 
than did those wdiich emerged after the middle of the emergence 
period. It is a common occurrence for weevils to leave their winter 
quarters upon warm days in spring, returning again to a condition 
of inactivity for a period of several days or even weeks. Disappear- 
ance and reappearance in the case of plainly marked indivitluals has 
been observed to occur as many as eight times, and a maximum 
period of forty-three days between appearances has been recorded. 
These facts argue very strongly indeed against tlie proposition w hich 
is sometimes made by those who are not thoroughly familiar with the 
habits of the weevil, to starve the emerged weevils by deferring the 
planting of cotton in the spring. Two lots of 20 and 8 weevils sur- 
90317— Bull. 77—09 7 



98 HIBERNATION OF THE COTTON BOLL WEEVIL. 

vived for an average ol" thirty and sixty days, respectively, after emer- 
gence without a particle of green food from the time of their entrance 
into hibernation to the time of their death. Other tests show similar 
results. 

The hibernation (^xi)eriments of 1906-7 consisted of lars-e-cao-e 
work in three localities representing the northern, central, and 
southern portions of the infested area. Each cage inclosed 10 sepa- 
rate experiments and the comparisons made possible b}' the three 
locations, the different shelter conditions, and the different dates of 
instituting the experiments furnish the basis for the most complete 
and significant work which has been done with the hibernation of the 
weevil. 

Owing to the exceptional mildness of this season, complete hiber- 
nation did not occur at any time during the winter in any part of 
Texas. Emergence began during the last week or ten days of Feb- 
ruary, 1007. At Dallas 7.8, at C^alvert 10.5, and at Victoria 27.7 per 
cent of the total numbers of weevils placed in the cages were counted 
as being active at some time during the winter season when they 
should normally have all been in complete hibernation. About 13 
per cent of the adult weevils buried with a lot of bolls under 2 inches 
of heavy, black soil escaped and were found upon the cage screen dur- 
ing the next few days. Weevils were active in the field as well as in 
the cages during this winter. The period of greatest emergence oc- 
curred during the latter part of March, which was undoubtedly from 
four to six weeks earlier than is usual. Succeeding low temperatures 
served to prolong the period of emergence until the 1st of July. In 
the three localities under observation an average of 11.5 per cent of 
the 75,000 weevils placed in the experiments survived and emerged 
in the spring of 1907. 

Orouping the experiments in the three localities according to the 
dates of installation of the weevils and averaging the percentages of 
survival in each group, it appears that there was a steady increase in 
this percentage upon succeeding tlates after the middle of October, 
when the experiments were started, to the end of November, when 
the last weevils were placed in the cages. This increase is so nearly 
regular as to prove conclusively that the date at which weevils are 
deprived of food in the fall, in its relation to the most favorable period 
for entrance into hibernation, has a most vital influence upon the 
prospect for survival. Among the weevils started October 14 but 
3.14 per cent survived, while among those started just one month 
later an average of 19.67 per cent survived. These results prove 
absolutely the advisability of destroying the food supply of the 
weevils at least three weeks before the usual time for the lu'st frosts 
to occur, and they show very plainly just why such a practice is the 



SUMMARY AND CONCLUSIONS. 99 

most effective niethotl yet found for reducing the number of weevils 
that may survive the winter to attack the crop of the following sea- 
son. This portion of the bulletin, especially, should be carefully 
studied in detail. 

The survival in the various sections of the cages in the three locali- 
ties ranged from 1.89 to 31.34 per cent. The average survival in 
each of the localities was as follows: Calvert, 9.49 per cent; Dallas, 
11.22 per cent; Victoria, 13.47 per cent. 

At Dallas the largest percentage of survival occurred in a section 
of the cage having an abundance of fallen leaves, in which the weevils 
were placed on November 15 and with the cotton stalks left standing. 
The smallest survival occurred in a section having fully as favorable 
shelter conditions but in which the weevils were placed on October 13 
and left without any food from October 15. 

At Victoria the largest survival occurred among weevils started on 
November 6 without food in the section provided with Spanish moss 
and bark. 

The winter was too mild to furnish any comparative test of the 
favorableness of various shelter conditions, but in general it appears 
that fallen leaves, Spanish moss, and a heavy growth of grass are 
most favorable to the weevils wherever they may occur. 

Temperature conditions were practically normal during November, 
1906, and the most favorable time for entrance into hibernation was 
between November 12 and 15 at Dallas and slightly later at the 
more southern points. 

In each locality the maximum longevity was shown by males, and 
the average duration of life of that sex was also slightly in excess of 
that of females. The average survival of all weevils kept without 
food was about ten days, and a considerable number lived to between 
six and twelve weeks after emergence. The maximum survival for 
any unfed weevil was ninety days. Obviously there is no chance to 
starve out all weevils by any possible delay in planting. 

Among the fed weevils the longest-lived was also a male which 
was active for one hunch'ed and thirty days after its emergence. 
The longest-lived female was active for one hundred and eighteen 
days. The average active life for all fed weevils was 25.5 days after 
emergence. Practically one-half of all fetl weevils lived for more 
than six weeks in the spring. 

The sex was determined for more than 8,500 weevils which had 
survived the winter, and it was found that 56.7 per cent of these were 
males. There is an invariable preponderance of males both in the 
fall upon entering hibernation and in the spring upon emergence 
therefrom. 

Reproduction can not begin until tlie first squares become at least 
half grown. At whatever date cotton may be planted in a locality, 



100 HIBERNATION OF THE COTTON BOLL WEEVIL. 

there is a decided advantage in having it all planted at as nearly a 
uniform date as is possible. As a rule early-planted fields yield better 
than do those planted later, but with similar conditions of seed, soil, 
and cultivation. All volunteer and sprout cotton developing in 
advance of the main crop should be destroyed before it forms squares, 
since otherwise it may furnish the weevils with opportunities for 
reproduction for some time before squares become common and 
thereby unnecessarily, early in the season, increase their numbers 
and the resultant injury to the main crop. 



O 



LIBRARY OF CONGRESS 

ODDDflflflHHSt, 



